Article Types

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.

Article

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.

Review

Reviews offer a comprehensive analysis of the existing literature within a field of study, identifying current gaps or problems. They should be critical and constructive and provide recommendations for future research. No new, unpublished data should be presented. The structure can include an Abstract, Keywords, Introduction, Relevant Sections, Discussion, Conclusions, and Future Directions.

A Scoping Review type can be submitted as a Review. The structure is similar to that of a review. Scoping reviews should strictly follow the PRISMA extension for scoping reviews checklist (https://www.prisma-statement.org/scoping) and submit the checklist as non-published material during submission. Templates for the flow diagram can be downloaded from the PRISMA website and the diagram should be included in the main text. We strongly encourage authors to register their detailed protocols, before data extraction commences, in a public registry such as the Open Science Framework (https://osf.io/) or Inplasy (https://inplasy.com/). Authors must include a statement about following the PRISMA guidelines and registration information (if available) in the Methods section.

Systematic Review

Systematic review articles present a detailed investigation of previous research on a given topic that use clearly defined search parameters and methods to identify, categorize, analyze, and report aggregated evidence on a specific topic. The structure is similar to a review; however, they should include a Methods section.

Systematic reviews should strictly follow the PRISMA checklist (https://www.prisma-statement.org/prisma-2020-statement) and include a completed PRISMA flow diagram as part of the main text or Supplementary Materials. Templates for the flow diagram can be downloaded from the PRISMA website. We strongly encourage authors to register their detailed protocols before data extraction commences, in a public registry such as PROSPERO (https://www.crd.york.ac.uk/prospero/). Authors must include a statement about following the PRISMA guidelines and registration information (if available) in the Methods section.

Brief Report

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.

Case Report

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.

Communication

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.

Hypothesis

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.

Protocol

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.

Project Report

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.

Registered Report

Registered reports are scientific articles which are peer reviewed before the research is performed and the data are collected. The ideas that meet high scientific standards, such as rigor, soundness, significant importance, and implications for the scientific community are then provisionally accepted for publication before data collection starts. Detailed guidelines for registered reports can be accessed here: https://www.mdpi.com/about/article_types/registered_reports.

Technical Note

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.

Essay

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.

Opinion

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.

Perspective

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.

Book Review

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.

Editorial

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.

Interesting Images

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.

Abstract and Proceeding Paper

These types of articles contain peer reviewed research output from conferences and can be submitted to one of MDPI’s proceedings journals: https://www.mdpi.com/about/proceedings.

Abstracts could be a short single paragraph summarizing the main topic and findings presented at the conference, or the extension of a typical abstract that contains a moderately detailed account of the work. They should be submitted to a conference in advance and provide details in support of a presentation made at the conference. The main text usually has no sections, but may include tables, figures, and references. The length should not exceed four pages.

Proceeding papers report new evidence or conclusions, and are expanded versions of work presented in a conference presentation. Conference proceedings can be incomplete findings that report on an idea, technique, or important results, thus providing readers with a brief overview of recent work or specific projects of significant interest. The structure is similar to a standard research article, and should include sections such as an Introduction, Methods, Results, Conclusions, etc. It is recommended that the length should not exceed eight pages.

Conference Report

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.

All published items will be assigned a digital object identifier (DOI) and be citable, and posters, videos, or PPT presentations can be published together as the Supplementary Materials.

For updating published papers, please see the descriptions for Corrections, Retractions, Comments and Replies, and Expressions of Concern online at Research and Publication Ethics.