Welcome to the MDPI style guide. Its purpose is to offer guidance and advice to authors intending to publish in an MDPI journal. Topics covered include formatting and conventions specific to MDPI and some tips for how to improve clarity and writing style.

This is a guide, not a set of instructions. English is a flexible language and most of its rules can be broken under the right circumstances. Our aim is to communicate the latest scholarly findings in a way that is accessible and readable. Most of the guidelines here are to aid clarity and precision. Where rigidly following this guide does not achieve that goal, exceptions can be made.

We do not expect authors to have strictly followed all of these guidelines when they submit their paper. Preparing a manuscript for publication is a key task of a publisher and includes applying the house style. Our editors will not reject a manuscript where the authors do not add a space before a unit of measurement or use the wrong tense to describe their experiment—at MDPI, we pride ourselves on providing a comprehensive production service prior to publication. Authors may benefit from reading and applying the conventions given here, though, as improving clarity and removing ambiguity can increase the chance of passing peer review.

This style guide is organized according to the sections of a research article. It begins with the front matter, which includes the title, article type, author information, and abstract. It continues with the main text, where the majority of advice on writing style can be found. There is a chapter on the presentation of mathematical content, followed by one on representations of data—including how to assemble tables and figures. Next comes information about the back matter, which includes various declarations by the authors and advice on writing the bibliography. Finally, there is a short section on publication ethics and how to revise and resubmit a paper.

The front matter covers parts of the article that usually appear at the top of the first page and give general information, including the title, abstract, journal name, and information about the authors. The format is standardized and much of it is added and formatted by the publisher.

All articles are assigned a type, depending on the content of the article. This is useful to readers, informing them of the style of content to expect (original research, review, communication, etc.) and for indexing services when applying filters to search results. This section details the most common article types, although is not exhaustive. Editors have the final say on which type should be assigned to a published article. Scientists are encouraged to publish their experimental, theoretical, descriptive studies and observations in as much detail as possible so the results can be reproduced. Manuscripts that are not comprehensive may be found not suitable for peer review.

These are original research manuscripts. The work should report scientifically sound experiments and provide a substantial amount of new information. The article should include the most recent and relevant references in the field. The structure should include an Abstract, Keywords, Introduction, Materials and Methods, Results, Discussion, and Conclusions (optional) sections. Please refer to the journal webpages for specific instructions and templates.

Brief reports are short, observational studies that report preliminary results or a short complete study or protocol. Brief reports usually contain two figures and/or a table; however, the Materials and Methods sections should be detailed to ensure reproducibility of the presented work. The structure is similar to that of an article.

Common in medical journals, case reports present detailed information on the symptoms, signs, diagnosis, treatment (including all types of interventions), and outcomes of an individual patient. They usually describe new or uncommon conditions that serve to enhance medical care or highlight diagnostic approaches. The structure of case reports differs from articles and includes an Abstract, Keywords, Introduction, Detailed Case Description, Discussion, and Conclusions. Special care should be taken when submitting case reports to ensure that appropriate permission for publication has been obtained from patients featuring in the paper. A sample blank consent form can be found on the ‘Instructions for Authors’ pages of the relevant journals. Please refer to the journal websites for more information, because not all MDPI journals publish case reports.

Communications are short articles that present groundbreaking preliminary results or significant findings that are part of a larger study over multiple years. They can also include cutting-edge methods or experiments, and the development of new technology or materials. The structure is similar to an article.

Conference reports are records of the events of a conference, seminar, or meeting. They should provide a comprehensive overview of a meeting or session, along with relevant background information for the reader. The structure should contain Abstract, Keywords, Introduction, Conference Sections, and Concluding Remarks. They can also include all accepted meeting abstracts.

These are non-peer-reviewed texts used to announce the launch of a new journal, a new section, a new Editor-in-Chief, a Special Issue, or an invited editorial. The main text should provide a brief introduction of the purpose and aim of the Editorial—to present the new journal, close the Special Issue, report on a pressing topic, etc. Editorials should not include unpublished or original data, although must provide a Conflict of Interest statement. Editorials prepared for the launch of new journals may also include a short biography of the Editor-in-Chief.

Essays are an article type commonly used in humanities and social sciences to present provocative arguments aimed to stimulate the readers’ re-thinking of certain issues. The structure is similar to that of a review. Arguments should be supported by relevant references.

Hypothesis articles introduce a new hypothesis or theory, or a novel interpretation of that theory. They should provide: (1) a novel interpretation of recent data or findings in a specific area of investigation; (2) an accurate presentation of previously posed hypotheses or theories; (3) the hypothesis presented which should be testable in the framework of current knowledge; and (4) the possible inclusion of original data as well as personal insights and opinions. If new data are presented, the structure should follow that of an article. If no new data are included, the structure can be more flexible, but should still include an Abstract, Keywords, Introduction, Relevant sections, and Concluding Remarks.

This article type presents interesting images selected for educational, diagnostic, illustrative or aesthetic purposes. The number of images included is at the discretion of the author and there are no restrictions on use of color or image size; however, high-resolution images with sharp features must be provided. The structure of Interesting Images includes an unstructured Abstract and Keywords with no regular manuscript text (introduction/methods/results/discussion). Images should be accompanied by detailed legends focusing on the features of the image and their relevance, not a report of a case study. Reference citations should appear in the legends. There are no length restrictions on the legends.

Opinions are short articles that reflect the author’s viewpoints on a particular subject, technique, or recent findings. They should highlight the strengths and weaknesses of the topic presented in the opinion. The structure is similar to a review; however, they are significantly shorter and focused on the author’s view rather than a comprehensive, critical review.

Perspectives are usually an invited type of article that showcase current developments in a specific field. Emphasis is placed on future directions of the field and on the personal assessment of the author. Comments should be situated in the context of existing literature from the previous 3 years. The structure is similar to a review.

Project reports are short and/or rapid announcements of project results and implications. They should include a research strategy or approach, the activities, technologies, and details of the project undertaken, conclusions, and recommendations for the future direction of work in the field. The structure is similar to an article, but permits a higher degree of flexibility.

Protocols provide a detailed step-by-step description of a method. They should be proven to be robust and reproducible and should accompany a previously published article that uses this method. Any materials and equipment used should be explicitly listed. Conditions, quantities, concentrations, etc., should be given. Critical timepoints and steps, as well as warnings, should be emphasized in the text. The structure should include an Abstract, Keywords, Introduction, Experimental Design, Materials and Equipment, Detailed Procedure, and Expected Results.

Technical notes are brief articles focused on a new technique, method, or procedure. These should describe important modifications or unique applications for the described method. Technical notes can also be used for describing a new software tool or computational method. The structure should include an Abstract, Keywords, Introduction, Materials and Methods, Results, Discussion, and Conclusions.

Book reviews are short literary criticisms analyzing the content, style, and merit of a recently published book. Full book details should be provided at the beginning of the article. The structure should only include an Introduction and be a discussion of critical points with no sections or conclusions.

There are few rules about the titles of submitted papers; however, there are some points that authors should keep in mind. The title conveys the main topic of the research and normally includes the principal results. It should be concise, descriptive, and grammatically correct. Periods should be avoided; instead, authors can use commas, colons, or en dashes. Italics should only be used where they are required for specific nomenclature (such as species names or journal titles) but should not be used for emphasis.

We recommend that authors keep their audience in mind and try to appeal to as broad a readership as possible. Therefore, avoid abbreviations and jargon that those outside of your field may not understand. Creative and original titles can be used, but make sure they do not sacrifice clarity in an effort to be eye-catching. Running titles should be avoided.

Some article types, including Corrections, Retractions, and Expression of Concern, have specific formats for the title that must be followed. We also strongly recommend this format for Comments and Reply, although authors may submit an alternative title, which will be used at the discretion of the editorial office. An example of the standard format is as follows:

Correction: Nasonova et al. Linking Regional Winter Sea Ice Thickness and Surface Roughness to Spring Melt Pond Fraction on Landfast Arctic Sea Ice. Remote Sens. 2018, 10 , 37

For titles of Comments, the following is an example of the standard format without a comment title:

Comment on Tanmoy et al. CRISPR-Cas Diversity in Clinical Salmonella enterica Serovar Typhi Isolates from South Asian Countries. Genes 2020, 11 , 1365

Titles of book reviews should have the following format:

Book Review: Microbiology in Dairy Processing: Challenges and Opportunities ; Poltronieri, P., Ed.; IFT Press Series: Wiley-Blackwell, UK, 2017; ISBN: 978-1-119-11480-2

In order to identify who wrote the paper and contributed to the work, author names and affiliations are displayed at the beginning of a paper. More details about qualification for authorship and author roles are given in the section on author contributions.

It is very important that author names and affiliations are correct. Incorrect information can mean a lack of proper attribution or incorrect citation and can even lead to problems with promotion or funding.

The publisher attempts to verify the authors’ identities and where necessary will make contact with the authors to confirm details. Misrepresenting affiliations is extremely serious and may constitute fraud.

Below are some important points about author names:

Affiliations should be those that the authors had at the time the work was carried out. The main role of the affiliations is, as far as possible, to unambiguously identify the authors. Please pay attention to the following important points about affiliations:

We strongly recommend that authors have an ORCID account (see orcid.org), which is a unique identifier for scholarly researchers. Your ORCID can be added in the submission system and will be included in the final version of the paper with an icon linking to your online ORCID profile.

We also strongly recommend that authors have a SciProfiles account (see https://sciprofiles.com/), which is a social network for researchers and scholars. It will help you find relevant publications and conferences and keep you updated with the latest events in your network. Your SciProfiles can be added in the submission system and will be shown on the paper’s homepage with an icon (before each author name) linking to your online SciProfiles.

The abstract contains a summary of the entire paper and can be up to 200 words long with only one paragraph. It must not contain any images or tables (although a graphical abstract may also be submitted). Do not included running title, website links, equations, figures (or other graphical elements), tables, or structures that require display on a line separate from the text.

Authors should follow the style of a structured abstract, which is based on the IMRAD structure of a paper but without using headings. In other words, give a background and motivation to the paper, a brief description of the methods, the principal results, and then conclusions or interpretations. Some journals in the medical field may require subheadings within the abstract; you may refer to the instructions for authors to see if this is required. Abstracts without headings should consist of a single paragraph.

Abstracts must be self-contained: they are often displayed and read independently of the rest of the paper. This means that any abbreviations used must be defined in the abstract, and no reference can be made to the bibliography or any figures. Citations to previously published papers are not required in abstracts.

The abstract, along with the main title, is the first part of your paper that a reader will see. It should give them a good overview of all the major aspects of the work carried out. It should not be thought of as a sales pitch to encourage readers to download and read the full article, although including some motivation is a good idea. Instead, you should focus on making it informative and comprehensive. A well-written abstract will mean that someone who goes on to read the full article will already have a good idea of the content and will be able to focus on the parts they are most interested in.

A graphical abstract (GA) is an image that appears alongside the text abstract in the Table of Contents. In addition to summarizing the content, it should represent the topic of the article in an attention-grabbing way. Note that the GA must be original and unpublished artwork. Any postage stamps, currency from any country, or trademarked items should not be included in it. The detailed requirements for a GA are listed below.

A Digital Object Identifier (DOI) is a unique number registered through a central organization, usually CrossRef for journal articles. Its role is to act as a persistent identifier, meaning that if the URL of an article changes, the DOI can still be used to find its most recent location. The DOI is defined by the publisher.

In addition to the DOI, MDPI also issues pagination for articles. This includes several numbers or series of letters that identify where and when the paper was published:

Except for the ISSN, these numbers occur in citations, e.g., Sensors 2013 , 13 (6), 6910–6935. Note, however, that the MDPI reference style omits the issue number (see the section on references).

The license determines how the work can be used after publication. MDPI articles are published using a creative commons CC BY license, meaning that the work may be reused—either in full or in part—without restriction, provided that the original source is acknowledged. In practice, this means that anyone using the article must cite it and thus give recognition to the authors. The terms of this license are what makes the articles open access. A different open access license may only be used in exceptional circumstances and must be approved at the submission step by the editorial office.

The next few sections cover the main text of an article, which is written almost entirely by the authors. For research articles, this is where details of the experiments and results are presented. The main text may be supplemented by additional documents or sections, such as appendixes and supplementary material. Accession numbers, URLs, or DOI URLs can be used to refer to data or code hosted on other websites.

Research articles have a standard structure, which is set out in the instructions for authors of the journal and the journal template. The majority of journals use a so-called IMRAD structure, meaning that the sections are Introduction, Materials and Methods, Results, and Discussions. Some journals require a Conclusions section at the end, and others have the Materials and Methods section after the Results and Discussions. Authors may choose to have Results and Discussions as one or two sections.

Review articles, essays, and other article types usually have a different structure, which is often more flexible. There should, however, still be a logical pattern. We recommend that the structure of an article is still considered, so the paper firstly presents a motivation for the work, followed by relevant data and previous work, and gives conclusions at the end. For systematic reviews, the structure should more closely follow that of a research article, with the methods describing how literature was chosen for inclusion.

Figures, tables, and schemes should appear in the text shortly after the first time they are cited. Where possible, they should be in the same section as the citation. It is not necessary to add them at the top or bottom of a page, and they should not break paragraphs. However, authors do not need to strictly follow these rules, and the production team will determine the most appropriate placement of figures. Note that there may be some adjustments in figure placement between author proofreading and final publication. Further details about adding these elements are given below.

There are no specific requirements from MDPI regarding the structure of paragraphs, but they should follow conventions for English writing. Paragraphs should contain and develop a single theme. They should be self-contained, which means, for example, that you should not use pronouns (it, he, she, they) referring to previous paragraphs.

A recommended structure for paragraphs is first to introduce the main idea, then give further relevant details, and finally to give interpretations or conclusions. This structure gives clarity to readers: if the idea contained in a paragraph is not clear from the start, there is more chance for misinterpretation. In some subjects, particularly in the humanities, an alternative structure may produce a particular effect on the reader that the author is trying to create; however, we recommend that care be taken to ensure that the message is as clear as possible.

For research articles, the headings are defined. For other types of paper, the authors have more flexibility to choose the headings. You may use up to three levels of headings/subheadings. Section headings are numbered, with first-level headings as, e.g., 1.; second-level heading as, e.g., 1.2.; and third-level headings as, e.g., 1.2.3. (as in this guide). Any headings used in a fourth level may simply appear as a paragraph with no indentation. In this case, though, we recommend reassessing the section definitions to see whether only three levels could be used. Headings without numbers may also be used to introduce a series of different cases. See the mathematics section for certain special environments with their own heading styles (e.g., Theorem, Proposition, and Proof).

Headings are written using title case, which means that the first letter of all words is capitalized with the exception of short words, including articles (a, the, etc.), and all prepositions (before, after, through, under, etc.). Pronouns (he, she, it, etc.) should be capitalized, as should prepositions used in compound words (e.g., set-up). Capitalize each component of compound words if the component would be capitalized when standing alone (e.g., Half-Life and Cross-Link).

Italicized species names should not be capitalized (e.g., in Escherichia coli ). The first word of the title and the first word after a colon or em dash should be capitalized regardless of the previous rules.

When writing symbols, use common, standard fonts where possible. If you are using a template in Microsoft Word, ensure that the font is correctly set for all text, especially when copying and pasting text from a different document. The format painter tool can help.

Avoid using fonts such as symbol, wingdings, or webdings. Authors should also avoid adding symbols as pictures, as this can lead to difficulties in formatting the final version. If there is a symbol you have difficulty in adding, leave a comment in the text so that the production team can take note.

For LaTeX, we recommend using an editor that includes a good list of symbols in the menus and a spell checker. This increases accuracy in writing and decreases the need to memorize many different codes. Table 1 contains LaTeX codes for a few especially useful symbols.

Table 1. Commonly used LATEX symbols.

Most abbreviated phrases should be written in full the first time that they are used, with the abbreviation in brackets, for example, “small angle X-ray scattering (SAXS)”. Some very common abbreviations do not need to be defined—some of these are universal and others depend on your intended audience. Below are a few common abbreviations that usually do not need defining. Non-standard abbreviations for phrases that are commonly used throughout an article can be defined, but avoid redefining abbreviations that already have a more common meaning. Words used in abbreviations do not need to be capitalized, even if the abbreviation is capitalized.

Note that the abstract, main text, and figure/table/scheme captions are treated separately for abbreviations. This means that you need to define the abbreviation the first time you use it in each part—you may have to define the same abbreviation three separate times. The reason for this is that they are often displayed in isolation; for example, indexing services usually only display the abstract and you can browse figures without the main text via the journal website.

Table 2. Common abbreviations that do not need defining in the text. This list is not exhaustive, and you may still choose to define these abbreviations for clarity.

The following Latin abbreviations may also be used in text: etc. (et cetera), to indicate that a list is incomplete; i.e., (id est), meaning “in other words” to add clarification to a phrase; and e.g., (exempli gratia), meaning “for the sake of example” to introduce a list of examples. Note that it is not necessary to use, “e.g.” and “etc.” in the same list. Confusion between “i.e.” and “e.g.” is common—if your list of examples is complete, then use “i.e.” but if there are additional cases not mentioned, then use “e.g.” Both “e.g.” and “i.e.” should be followed by a comma and do not need to be italicized.

Do not abbreviate “also known as” to “aka” or use an ampersand (&) instead of “and”—they should be written in full.

Authors may use italics for emphasis at their discretion. Be careful that there is no confusion, especially in disciplines where italicization is used for another purpose, such as in mathematical symbols or gene names.

Foreign words do not need to be highlighted or italicized, including Greek/Latin terms, such as i.e., e.g., etc., et al., vs., ca., cf., in vivo, ex vivo, in situ, ex situ, in vitro, in utero, ad hoc, in silico, ab initio, vice versa, and via. Authors may choose use italics for purposes of emphasis or where a term is being defined. Journal and book titles should always be written in italics, e.g., International Journal of Environmental Research and Public Health .

Italics must be used for the genus and species when using Latin names of organisms. The first time the name is used it should be spelled out in full, but for further uses, the genus can be abbreviated to the first letter. Note that the species is always written without a capital letter, including when it appears in a title; the genus name should always be capitalized. Similarly, italics should be used for gene names (but not for the corresponding proteins). Examples:

Escherichia coli is a common bacterium ... E. coli was used in this article.

Lac1 is the gene that encodes for the Lac1 protein.

Bold font should generally be avoided. If you wish to add emphasis, italics are preferred. Bold font is used in specific contexts, including figure captions and subtitles. In chemistry, bold numbers can be used to refer to molecules defined in Schemes.

Any text taken from previous work, whether published or not, should be clearly indicated. The recommended way to do this is as a quotation accompanied by a citation and bibliography entry. Quotations should appear in double quotation marks (“ . . . ”). Long quotations may appear as a block quotation: a separate paragraph set off from the rest of the text with an indent on both sides. The exact formatting will be completed by a layout editor during production.

Most scientific journals from MDPI do not allow notes. Check the instructions for authors of the journal to see the specific policy of a journal.

Where notes are permitted, they may be used to add additional explanatory notes to text. All notes will be shown in the Notes section, which is before the References section. Information essential to understanding the text should not be added to notes. They can be used to add additional sources, explain the background to a particular point, reinforce ideas, or clarify intended meaning. Notes should not be used as a replacement for a bibliography, since citations included only in notes will not be detected and counted by indexing services.

Most lists can be included as inline text; however, authors may decide that the information is more clearly represented using bullet points. If there is a specific order to the list, a numbered list may be used. A descriptive list may also be used, in which each item begins with an emphasized word or short phrase.

For inline lists, items should be separated by commas. An exception is where one or more items contains a comma, in which case semicolons can be used. Do not use commas for lists of two items. Serial (or Oxford) commas are recommended; however, they may be omitted if done so consistently, especially when not using American English for spellings.

For itemized lists, introduce the list with a colon, add a semicolon at the end of each item, and a period at the end of the last item. Alternatively, periods may be used at the end of each item. Always capitalize the first word of each item.

Examples of lists. Using bullets:

A numbered list:

A descriptive list:

Item 1 the first.
Item 2 the second.
Item 3 the third.

Note that lists that mention that only a few examples are given do not need to end with ‘etc.’, ‘and so on’, or similar text. Doing so means that you have indicated twice that the list is incomplete. For example:

Examples include red, white, and green varieties.

Popular varieties are red, white, green, etc.

Authors may declare any patents related to the published work, either those pending or already obtained. The aim of this section is to create a better link between research articles and new inventions to which they have contributed. This section is not obligatory, and there is no penalty for not declaring patents, but in most cases authors benefit from adding any relevant information here.

When declaring patents, please include the patent number and title so that any interested readers can access the full details.

We strongly recommend against submitting papers for publication before patents have been granted, since publication can compromise the patent application process. Published papers will not be removed from journals in order for patent applications to be filed.

In scientific writing, the language around what is already known and what remains unknown needs to be precise. This relates to the passage of time and hence the use of tenses. The following looks at how tenses are used in each part of a research paper.

In the introduction, current problems and past work are typically discussed, along with a description of what the paper presents. The authors should use the present tense to describe outstanding problems:

“The increase in the number of RF electromagnetic sources is associated with a growing concern about potential harmful health effects of human exposure to RF radiation.”

Former work can be in the past or present tense:

“These uncertainties are due to the directivity of the body-worn antennas [5], or body shadowing in which the body shields part of the EM fields.”

“In [4] it was shown that the location of PEMs contributes to the uncertainty of their measurements and results in an underestimation of the incident electric fields.”

New results being presented by the authors should be in the present tense (not future):

“The designed antennas and the frequency bands of the BWDM are summarized in Section 2.2. Section 2.3 presents the design of the receiver nodes.”

Methods should typically be presented in the simple past tense:

“The multi-antenna measurement system consisted of 22 autonomously working measurement units, for 11 different frequency bands, connected to a common serial bus system.”

An exception is where methods are described in the form of instructions or an algorithm. These are most often used in theoretical papers:

“The following describes the calibration procedure. First, place the subject (Sb-1) on a rotational platform in the far field of a transmitting horn antenna (TX) in an anechoic chamber.”

The present perfect should be avoided:

“The subject has been placed on a rotational platform . . . ”

This is the section where tenses are most often mixed and there is more flexibility/ambiguity about the correct tense to use. As a rule, established facts should use the present tense; however, difficulty arises when a single result is presented as establishing a fact. Authors may write the same phrase in different ways:

“The results show that commercial PEMs underestimate the actual incident power densities by a factor of 1.6 to 20.6.”

“In our study, commercial PEMs underestimated the actual incident power densities by a factor of 1.6 to 20.6.”

“Commercial PEMs underestimate the actual incident power densities by a factor of 1.6 to 20.6.”

The first example uses the present tense because the results are fixed and will not change in the future. The second uses the past tense, much like the methods section, to describe what happened during the experiments. The third is a bolder statement that generalizes the results of the paper to all commercial PEMs.

The second is the best option as it is a clear statement of what happened during the current study. Anything that speculates or extrapolates the results should be clearly differentiated. For example:

“In our study, commercial PEMs underestimated the actual incident power densities by a factor of 1.6 to 20.6. This could imply significant measurement errors where PEMs are used in an industrial environment.”

This phrasing separates the third statement above into two distinct phrases that differentiate the results from the conclusions.

In a review, the writing often jumps rapidly between established facts, the results of studies, and speculation. Paragraphs or sections can be a microcosm of a complete paper, firstly setting out a problem, describing work done, and then making a conclusion about the current state of the field or speculating on the future. Be aware of which tense is appropriate for each statement:

“Smartphone imaging is used extensively in remote sensing, for example in aerial photography and grass roots mapping applications . . . It has been applied quantitatively, for example in determining ‘leaf area index’, which is a measure of foliage cover [18], and could offer powerful tools for tracking longer term trends in sky [19], land cover and vegetation conditions.”

There are different writing styles for reviews, such as using references to support a stated fact, written in the present tense:

“LOD is defined as the smallest concentration of an analyte that can be reliably detected, where reliable detection means the sensor response should be different from that of blank/reference [27].”

Alternatively, the authors may describe work done, similar to a methods section:

“A microstrip coupled CSRR has been proposed as a chemical sensor [34]. In this setup, the microstrip line is designed on the top of substrate and CSRR is etched on the bottom ground. Withayachumnankul et al. [33] varied the concentration of water–ethanol solution, and the corresponding S-parameters were measured. To validate the proposed sensing system, the measured complex permittivity values of mixture were compared with the reference ones. This sensor showed four times higher sensitivity compared to their previous work.”

It is authors’ responsibility to differentiate established facts from speculation through the use of tenses. Use of tenses should be consistent throughout a manuscript in order not to confuse readers.

(Quotations in this section adapted from Sensors 2018 , 18 , 272; https://doi.org/10.3390/s18010272, Sensors 2018 , 18 , 232; https://doi.org/10.3390/s18010232, and Sensors 2018 , 18 , 223; https://doi.org/10.3390/s18010223.)

Plurals need to agree with other parts of the sentence; this is an area where errors often occur, particularly in complex phrases. For example:

“The full implementation of the trained networks are available at”

should be

“The full implementation of the network algorithms is available at”

since the verb agrees with “implementation”, not “networks”.

The word “data” should be considered to be plural, so write “The data show that . . . ” rather than “The data shows that . . . ”. The singular form is “datum”.

In MDPI papers, US, British, or other variations of English can be used; however, authors must be consistent throughout the paper. We recommend that authors use American English unless they live or work in a country that uses a different variation (e.g., the UK, Australia, or Canada).

One of most notable differences between British and US English is the use of -ise instead of -ize as a suffix. Some words are spelled differently; a few examples are

A good spell-checker can help to identify words that are incorrectly spelled and authors should set the proofing language in their writing software to the version of English they wish to use.

Articles can include text written in languages other than English provided that a translation is provided. This includes labels used in figures. Note that non-English words or phrases do not need italicizing.

Authors should have a good knowledge of standard punctuation. This guide is not intended to be comprehensive and authors should refer to textbooks to ensure the correct use of punctuation. In this section, we highlight aspects that particularly reflect the MDPI style.

Periods that end sentences should be followed by a single space. Most abbreviations use periods to indicate where letters have been omitted. Note that “vs.” should be followed by a period, except in papers covering law, where the convention is to omit a period.

There are four types of dashes used in writing:

When using prefixes and suffixes, hyphens are not required unless omitting them creates ambiguity in the meaning or double letters. Some words are conventionally written with or without hyphens, and for others, multiple forms are in common use. You will not be expected to know all of these and the editorial team will check before publication. A few examples are

Prehistoric, lifelike, anti-inflammatory, and un-ionize.

For compound adjectives, hyphens should typically be used. Two words together used to modify a single noun are termed “unit modifiers”. Note that hyphens should also be used in double-barreled names. For example:

Three-dimensional, time-dependent, Parker-Bowles, and grey-green. Chemical names, however, should not be hyphenated (e.g., sulfuric acid).

En dashes can be used to denote a chemical bond, a range between two numbers, or a relationship between two separate entities. They are also used between the last names of two different people when their names are used for a scientific concept. Some examples:

Carbon–oxygen bond

A time–frequency plot

17–30 m in length

Fabry–Perot

Bose–Einstein

For MDPI papers, em dashes are preferred to colons when introducing phrases that provide clarification or definitions. Spaces should not be included either side of em dashes. For example:

“We measured alignment using linear dichroism—differential absorbance in perpendicular directions.”

We recommend using em dashes sparingly to avoid disrupting the flow of sentences.

As mentioned above, em dashes are preferred to colons for introducing definitions. Colons may be used to introduce lists or before equations, but not where they separate a verb and its object or a preposition and its object.

Semicolons may be used in lists, as mentioned above. For other uses of semicolons, refer to a grammar book. In general, we recommend using semicolons sparingly and considering whether a period or comma would be more appropriate.

Apply the common usage of apostrophes to indicate ownership or contraction of words, although note that most contractions should be written in full (“cannot” instead of “can’t”, “it is” instead of “it’s”, etc.). Do not use apostrophes to pluralize abbreviations or numbers, e.g.,

“The results of five PCRs are shown.” “This was common practice in the 1960s.”

Numbers should usually be written as digits, with a few exceptions. Where there are five or more digits to the left of the decimal point, use a comma to separate every three digits, e.g., 123,456 or 153,958.9476. As in the previous sentence, numbers 0–9 should be written as words unless they are a measurement, i.e., they are accompanied by a unit. For example:

five trees

5 m from the tree

If a sentence starts with a number, the number should always be written out in full; however, it is often better to reword the sentence. As an example:

. . . and was heated. One hundred and seventeen grams of NaCl was added to the mixture.

However, this could be reworded as:

. . . and was heated. A total of 117 g NaCl was added to the mixture.

When writing about measurements, use a space between a number and its unit. SI or SI-derived units should be used where possible; if you use alternative units, please explain to the editors why it is necessary. Middle dot (always use middle dot as multiple sign in units) or a normal space can be used in units; however, they must be consistent throughout the paper. For example:

3 × 10 ⁸ m·s ⁻¹ .

Do not leave a space before a percentage (%) symbol, since the symbol is part of the number and not a unit. The same applies to degree (°) symbols when used for angles, so write 90° but 90 °C.

A space is optional between wt%, mol%, vol%, at% or wt.%, mol.%, vol.%, at.%, but keep the format consistent within a paper. Other formats are not allowed, e.g.,wt %, % wt.

For some common time units and measurement units, it is recommended to use abbreviated units if Arabic numerals are in front of them.

Table 3. Abbreviated SI Fundamental Units.

Powers of 10 can be indicated by a prefix to a unit. The following table shows terms that can be used in this way. For example, 1 pm = 1 × 10 − 12 m.

Table 4. Prefixes to units that indicate powers of 10.

Times should be written using the 24-hour clock with a colon between the hours and minutes, e.g., 12:42. Dates should be written with the format day (as a digit) month (as a word) year (four digits), e.g., 1 January 2001. BC (before Christ) or AD (anno domini) can be added if necessary; CE (Christian era) and BCE (before the Christian era) are also acceptable. Where other calendars are used (e.g., lunar calendars), we recommended including the date using the Gregorian calendar as well.

Mathematical symbols that appear between two numbers should have a space on either side, such as in “a = 2b”. Do not leave a space around mathematical operators in subscripts and superscripts, e.g., a _{n +1} , and also do not leave a space around other expressions in subscripts and superscripts, unless doing so would lead to confusion or misreading, e.g., E ^{365 nm} . Do not leave a space where there is only one number, e.g., “the number of samples in each case was >50”. Do not include a space when writing ratios, e.g., 1:100. Decimals need to be completed; e.g., a = .01 should be written as a = 0.01. Use scientific notation, i.e., a × 10 ^b rather than aEb or aeb. Leave a space before or after trigonometric function, e.g., cos Θ, cot Θ, sin Θ, tan Θ, sec Θ, csc Θ, etc.

You may include appropriate equations in your manuscript. They may be included inline or as a separate paragraph. Non-inline equations may be numbered starting from 1 (do not include a section number), e.g., Equation (1). In the appendixes, all equations should be prefixed with A and in the supplementary information with S, e.g., Equation (A1), Equation (S1). Subequations are not recommended; if necessary, they should be cited, for example, as Equation (1a). Minor or trivial equations do not necessarily need to be numbered, at the discretion of the author. In derivations involving multiple steps, obvious intermediate results may be omitted.

Punctuate equations as part of a regular sentence. For example, if the equation comes at the end of a sentence, a period should be placed immediately after the equation. It is not necessary to always use a colon to end the paragraph before an equation. If the equation is followed by “where . . . ” to define the symbols used, “where” should be all lower case and flushed to the margin (without first line indentation) to indicate that it does not begin a new paragraph.

All terms used in an equation should be defined in the text. It is highly recommended to check specifically for this during proofreading before submission, as undefined terms could lead reviewers and editors to misinterpret your meaning. Additionally, be aware of multiply defined symbols, and we recommend using standard notation in the field where it exists (e.g., P for a probability function). The format (italics/non-italics) of each character in an Equation should be consistent with the main text. Symbols used in equations should use italic font, although exceptions will be permitted where there is a convention not to use italics. Words and numbers in equations should not use italic font, for example,

P ( x ) = 2 a if x > 0.

The final formatting of equations will be done by MDPI staff. To assist them, take note of any examples in the journal template. In Microsoft Word, make sure your equations can be edited using the standard Word equation editor, rather than appearing as a picture. The content of one equation should be in the same environment (written in plain text or Word equation editor). Formatting is sometimes changed during production, and errors may be introduced if the equation appears only as a figure. LaTeX is convenient for writing equations. Users of LaTeX should try, where possible, to use common packages for introducing symbols, since this will make the production process more straightforward and error-free.

Papers that report mathematical proofs have a structure that differs from other kinds of research papers. They usually contain a short motivation and introduction followed by a series of logically argued results (lemmas, proofs, corollaries, etc.) intermingled with some examples, remarks, and definitions. In principle, these environments could be used by authors from any field, but it is recommended only to use them for mathematics, as some readers may not be familiar with the structure. The following environments may be used for mathematical content: Theorem, Lemma, Corollary, Proposition, Characterization, Property, Problem, Example, Examples and Definitions, Hypothesis, Remark, and Definition. Any mathematical environments should be labeled with an Arabic number and numbered sequentially.

The ‘Proof’ environment may be used for (mathematical) proofs of results. If they immediately follow the result, there is no need to state which result they refer to. If they appear later, the type and number of the result should be referenced, e.g., “Proof of Theorem 3”. This can be automated in LaTeX using the \label and \ref commands. Proofs may finish with a square box or “Q.E.D.”—the LATEX proof environment automatically adds the former.

Note that the MDPI LATEX class file automatically loads the amsmath and amsthm environments packages, which contain many commonly used symbols. You can see comments in the preamble of the MDPI LATEX template for more details.

Figures are graphics that support the main text. They may show data, an algorithm, a model, an image, or any other pictorial representation. Figures must be clear and readable, and we recommend a minimum resolution of 600 dpi. Any common figure formats may be used, including (but not limited to) tif, jpg, and png. For CAD and similar formats, a representation as, for example, a png file may be included in the text and the full original file included as supplementary material.

Others notes on figures:

Note that the production process may change the type of your file, and all files will be published in tif format. This should not affect the quality of your figure; however, if you notice a decrease in the quality after publication, you should contact the editorial office as soon as possible.

For figures with more than one part, the panels should be labeled a, b, c, d, etc., and each part can be separately cited in the main text. Each part must be individually described in the caption. It is recommended to use label “A, B...” or “a, b...” instead of “left, right, top, bottom” for the subfigures.

Captions are mandatory and are added below figures.

Long lists of categorized data may be added as a table. This could be done, for example, where there are many cases with similar information or many numerical data.

Tables will be reformatted to the standard MDPI style prior to publication, and the journal template provides an example. Use of color (including the color of table background and texts) is not recommended in tables but may be accommodated where necessary; if necessary, colors must be described in an image or a caption. Similarly, merged cells may be included but should be used sparingly, and it must be clear which rows/columns correspond to each other. Do not supply tables as images—they must be editable by MDPI staff.

Subtables are not recommended; if necessary, subtables could be numbered by Latin letters with parentheses, e.g., (a), (b), (c), etc., or (A), (B), (C), etc., which should be put before the table. Additionally, use the format of Table 1a,b in the main text.

A table footnote can be added to explain material referring to the whole table and to specific entries, and it usually comprises one paragraph. A hyphen may be inserted into a table body cell to stand for “None”: such an entry does not need further explanation in the table footnote.

Very large tables, or many different tables showing similar cases, may be included in an Appendix or as supplementary data.

Captions are mandatory for tables and are placed above the table.

Others notes on tables:

A box is equivalent to a table with a single cell. They are typically used to describe a case study that illustrates and supports some aspect of the main text. Boxes must include a caption, placed above. Each box should be marked by continuous numbers and cited in the main text. Boxs should be editable; do not use uneditable images.

Schemes are common in chemistry to define the synthesis of a chemical. They can be included in a similar manner to figures. Carefully verify that the structures given are correct. It is not usually necessary to include hydrogen molecules in schemes. Captions are mandatory for schemes and are placed below the scheme. Each scheme should be marked by continuous numbers and should be cited in the main text.

Algorithms are typically used in computing to explain a series of steps performed in a calculation or program. They may simply be included in the main text, but can also be numbered for easier citation. Use of monospace font is common for algorithms but not mandatory. A caption must be included above the algorithm. Each algorithm should be remarked by continuous numbers and should be cited in the main text. Algorithms should be editable; do not use uneditable images.

As mentioned above, captions are obligatory and must be placed above or below objects. They should provide a description of the object such that the reader does not need to refer to the main text to fully understand it. For example

is not helpful to readers, whereas

“The four methods used.”

is not helpful to readers, whereas

“The four minimization methods used to find the optimum parameters of the Navier–Stokes equation for three microfluidic devices.”

is better. Recall that figures and captions sometimes appear online separately from the rest of the article and so must make sense when not accompanied by the main text.

For previously published figures or tables, the necessary permission must be obtained from the copyright holder, except for publications with the open access license. The copyright permission can usually be obtained via an online form or by e-mailing the copyright holder. It is the authors’ responsibility to obtain the necessary permission.

In MDPI publications, credit lines for art reproduced from previously published work appear at the end of the caption in parentheses in one of two formats:

Format 1 (ACS Style)

For example,

Format 2 (Chicago Style)

For example,

If you adapt or use only part of a figure or table, permission is still needed. The credit line for adapted material is similar except “reprinted” is replaced with “adapted”, as below:

Format 1 (ACS Style)

Format 2 (Chicago Style)

For figures or tables previously published with the open access license, the copyright belongs to the author. The following description should be added at the end of the caption in parentheses in one of two formats:

Format 1 (ACS Style)

Reprinted from Ref. [X].

Adapted from Ref. [X].

Format 2 (Chicago Style)

Reprinted from Author Names (Year of Publication).

Adapted from Author Names (Year of Publication).

The back matter includes important information that supplements the main text and provides further information and context. Most of the back matter is provided by the authors, but the structures are quite standard.

The sequence of back matter elements in an article is listed below. Although each of them can be optional, very few articles have no reference list of some sort. There is no numeral label for back matter headings:

Additional data or information can be included in the supplementary material. Examples of information that can be presented as supplementary material include additional graphs, tables, original datasets, and computer codes. In most cases, authors are free to choose what is included as supplementary material. All materials should be provided in English (except for translations of the manuscript or abstract), and the provided version should be clean, without tracked changes, highlights, comments or line numbers.

There is also no restriction regarding file type, although we recommend using common, open file types that will remain readable in the future. There may be restrictions on file size for files hosted by MDPI; however, the editorial office will be able to offer alternative options if this is a problem.

Each author is expected to have made substantial contributions to the conception or design of the work; the acquisition, analysis, or interpretation of data; or the creation of new software used in the work; or they must have drafted the work or substantively revised it. In addition, each author must have approved the submitted version (and versions substantially edited by journal staff that involve the author’s contribution to the study) and agrees to be personally accountable for the author’s own contributions and for ensuring that questions related to the accuracy or integrity of any part of the work, even ones in which the author was not personally involved, are appropriately investigated, resolved, and documented in the literature.

Any research article describing a study involving humans should contain this statement. Written informed consent for publication must be obtained from participating patients who can be identified (including the patients themselves). Please state “Written informed consent has been obtained from the patient(s) to publish this paper” if applicable. You might also add “Not applicable” for studies not involving humans.