CSE citation style is a referencing system published by the Council of Science Editors in The CSE Manual, 9th edition (2024), the book earlier editions called Scientific Style and Format. It gives writers in biology and the other sciences three ways to cite sources: citation-sequence, citation-name, and name-year. Pick one system for a paper and use it consistently from the first in-text citation to the last reference list entry. This guide walks through all three CSE systems, shows the exact reference list format for the source types you’ll cite most often, and answers the questions students ask most about CSE citation style.
What Is CSE Citation Style?
CSE stands for the Council of Science Editors, the organization that maintains the citation style used most often in biology, ecology, and the other life and physical sciences. The style started in the 1960s as the Council of Biology Editors (CBE) format, built for editors of peer-reviewed biology journals. The organization renamed itself the Council of Science Editors in 2000, and the format took the new name with it. The 9th edition, published in 2024, renamed the manual The CSE Manual and trimmed its reference format: no place of publication before the publisher, no “[Internet]” or “Available from:” labels, and a DOI link at the end of online references. This guide follows the 9th edition.
The CSE Manual’s own citation quick guide is the authoritative source for the current 9th edition rules. If your assignment or target journal doesn’t specify which of the three CSE systems to use, most science departments default to name-year, since it lets a reader trace a citation back to its source without flipping to the reference list.
The Three CSE Citation Systems
Every reference in this style follows one of three documentation systems: name-year, citation-name, or citation-sequence. They produce different-looking in-text citations and sort the reference list differently, but the underlying source information you record for each entry is identical across all three. The table below compares how each system marks an in-text mention and orders the bibliography at the end.
| System | In-text citation | Reference list order |
|---|---|---|
| Name-Year | Author surname and publication year in parentheses, e.g. (Frog 1998) | Alphabetical by author surname |
| Citation-Name | Superscript number tied to the author, e.g. wing structure1 | Alphabetical by author surname, then numbered in that order |
| Citation-Sequence | Superscript number, e.g. wing structure1 | Numbered in the order each source first appears in the text |
Use only one system per document. Switching systems partway through a paper, or pairing a parenthetical name-year mention with a citation-sequence bibliography, is one of the most common formatting mistakes instructors flag.
In-Text Citations in CSE Style
An in-text mention in this style is either a surname with a publication year, or a superscript number, placed at the end of the sentence or clause that uses the work. The Council of Science Editors and most biology departments prefer paraphrasing scientific sources over quoting them directly, since paraphrased references read more naturally in a lab report or thesis. When you do paraphrase, see essayreply’s guide to paraphrasing for how to restate a source without drifting into someone else’s wording.
Name-Year In-Text Citations
In the name-year system, an in-text citation is the writer’s surname and the year of publication, either in parentheses or worked into the sentence:
- Research has shown that fly demographics affect flavor robustness (Frog 1998).
- As Frog (1998) demonstrated, fly demographics affect flavor robustness.
For a work with two writers, list both surnames joined by “and” (Frog and Toad 1998). For three or more contributors, give the first surname followed by “et al”, which takes no period in the 9th edition (Frog et al 2002).
Citation-Name and Citation-Sequence In-Text Citations
Both of these systems mark a citation with a superscript number instead of a name. The number placement is identical between the two systems. What differs is how the reference list assigns those numbers: citation-name sorts sources alphabetically first and numbers them after, while citation-sequence numbers sources in the order they first appear in your text.
Note: The in-text citation format doesn’t change based on how many authors a source has. Even a source with ten authors is still cited with one surname (plus “et al”) or one superscript number. The full author list only appears once, in the reference list entry itself.
Formatting the CSE Reference List
A handful of mechanical rules separate correctly formatted CSE references from references borrowed from another style, and the same rules apply whether you’re citing journals, books, or websites. Author initials never take periods. The last author’s name connects to the rest with a comma, not the word “and” or an ampersand. Book, journal, and website titles are written in sentence case, not title case, and are never italicized. Journal titles are abbreviated without periods (J Exp Biol, not J. Exp. Biol.). Each reference list entry uses a hanging indent, with the second and later lines indented under the first. Books name the publisher without a place of publication. Online sources end with their URL, a DOI link (https://doi.org/…) when one exists, with no period after it. If a web page has no publication or update date, write [date unknown] where the date goes and add the date you accessed it, as in [accessed 2026 Apr 7].
Correct CSE format: Frog RA, Toad JM. 1998. Expert’s guide to artisanal fly cuisine. 2nd ed. Imaginary Publishing Inc.
Incorrect (this is APA formatting): Frog, R. A., & Toad, J. M. (1998). Expert’s guide to artisanal fly cuisine (2nd ed.). Imaginary Publishing.
The differences are small but they matter to an instructor grading against a CSE rubric: no periods after initials, no ampersand, no italics on the book title, the year set off by periods instead of parentheses, and the edition written as a plain “2nd ed.” rather than in parentheses.
Citing Multiple Authors in CSE Style
CSE shortens long author lists the same way in every reference type. List every author by surname and initials, separated by commas, when a source has up to five authors. When it has more than five, the 9th edition lists only the first author followed by “et al”. This keeps the bibliography readable even when a journal article carries a large research team. When you cite that same article inside your essay’s body text rather than just the reference list, essayreply’s guide to citing an article in an essay covers how to introduce the source in your own sentence.
Note: Organizations can stand in for a personal author. A work published by the World Health Organization or the US Centers for Disease Control and Prevention is cited under the organization’s full name (or a recognizable short form) instead of a surname.
CSE Citation Examples by Source Type
The reference list format shifts slightly depending on what you’re citing. These examples use the name-year system. For citation-name or citation-sequence, number each entry and move the date: it follows the journal title for an article (Clim Dyn. 2020;54:3259-3277) and the publisher for a book (Elsevier Academic Press; 2004).
| Source type | General format | Example |
|---|---|---|
| Journal article | Author(s). Year. Article title. Journal title (abbreviated). Volume(issue):pages. DOI link or URL | Kim KY, Kim BS. 2020. The effect of regional warming on the East Asian summer monsoon. Clim Dyn. 54:3259-3277. https://doi.org/10.1007/s00382-020-05169-7 |
| Book | Author(s). Year. Title. Edition. Publisher. | Sorensen B. 2004. Renewable energy: its physics, engineering, use, environmental impacts, economy, and planning aspects. 3rd ed. Elsevier Academic Press. |
| Chapter in an edited book | Chapter author(s). Year. Chapter title. In: Editor(s), editor(s). Book title. Edition. Publisher. Page range. | Singleton P, Sainsbury D. 2001. Plasmid. In: Dictionary of microbiology and molecular biology. 3rd ed. J Wiley. p 593-594. |
| Website | Author or organization. Year. Title. Publisher; [date updated]. URL | National Agricultural Library (US). 2005. Animal welfare information center. National Agricultural Library. http://www.nal.usda.gov/awic/ |
| Newspaper article | Author. Year Month Day. Article title. Newspaper name. URL | Zimmer C. 2021 Apr 9. To speed vaccination, some call for delaying second shots. The New York Times. https://www.nytimes.com/2021/04/09/health/covid-vaccine-second-dose-delay.html |
| Conference paper or poster | Author(s). Year Month Days. Title. Paper or poster session presented at: Conference name; Location. | Charles L, Gordner R. 2005 May 14-19. Analysis of MedlinePlus customer service requests. Poster session presented at: MLA ’05: Medical Library Association Annual Meeting; San Antonio, TX. |
For most student essays covering a printed or online newspaper article, essayreply’s newspaper citation guide walks through the format across styles side by side.
How Does CSE Style Differ From MLA, APA, and Chicago?
CSE differs from MLA, APA, and Chicago style mainly in its numbered or name-year in-text citations and its science-journal reference formatting, which most humanities researchers rarely encounter. Most humanities and social science instructors expect MLA or APA instead, so double-check your assignment sheet before you pick a style. These guides cover the ground CSE doesn’t:
- Citation styles hub: see how CSE compares with MLA, APA, and Chicago at a glance.
- How to cite journals: format rules for print and online journal articles.
- How to cite books: book, edited volume, and chapter formats.
- How to cite a website: rules for undated pages and pages with no listed author.
Frequently Asked Questions
These are the CSE citation questions students and researchers run into most often: choosing between the three systems, formatting author names correctly, abbreviating journal titles, and avoiding the mistakes that get flagged on a graded paper.
How is CSE citation style different from APA’s name-year format?
Both use author-year in-text citations, but CSE drops periods after author initials, abbreviates journal titles without punctuation, and never italicizes titles, while APA italicizes book and journal titles and writes journal names in title case. The reference list layout and punctuation rules are different even when the in-text citation looks similar.
Do I put a period after author initials in CSE style?
No. CSE style writes author initials without periods, so “Frog RA” is correct and “Frog, R.A.” is not. This is one of the fastest ways to spot a reference that was copied from an APA or Chicago source without reformatting.
How do I abbreviate journal titles in CSE references?
Use the standard abbreviation from the ISSN List of Title Word Abbreviations, written without periods between words. For example, Journal of Experimental Biology becomes J Exp Biol. If you’re unsure of the standard abbreviation, most library databases list it next to the journal’s full title.
Which CSE system should I use if my instructor doesn’t specify?
Name-year is the most common default in biology departments because it lets a reader identify the source while reading, without flipping to a numbered list. Check your assignment sheet or the target journal’s author guidelines first. When in doubt, ask your instructor directly rather than guessing.
Can I mix CSE systems within one paper?
No. Pick one of the three systems described in The CSE Manual, name-year, citation-name, or citation-sequence, and use it for every in-text citation and every entry in your list of references. Mixing systems is treated as a formatting error, not a style choice.
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Terry is a Chicago-based writer and editor who creates practical, student-friendly guides on essay writing, research, and citation styles (APA, MLA, and Chicago). He’s spent 15+ years editing educational content and building clear examples that help readers apply rules without guessing. When he’s not revising drafts, he’s usually turning messy notes into clean outlines and hunting down the one detail everyone skips.