Most scientific papers use numbered citation systems rather than the author-date format common in social sciences. The exact style depends on your discipline: biology uses CSE, chemistry uses ACS, physics uses AIP, medicine uses AMA or Vancouver, and engineering uses IEEE. If you’re writing for a class or a specific journal, check their guidelines first, because even within a single field, journals sometimes pick different systems.
CSE Style for Biology and Natural Sciences
The Council of Science Editors (CSE) style is the default for biology, ecology, environmental science, and many other natural sciences. It gives you three options for how citations appear in your text, and your professor or target journal will specify which one to use.
Citation-Sequence is the most common. You place superscript numbers in the text as you cite sources, and the reference list at the end is ordered by when each source first appears. If the first source you cite is by Smith, that becomes reference 1. Every time you cite Smith again, you use the same superscript 1. An in-text passage might look like: “Linnaeus pioneered modern botanical nomenclature1, though other disciplines2,3 soon followed.”
Citation-Name also uses superscript numbers, but the reference list is alphabetized by author last name instead of ordered by appearance. So reference 1 might be Adams, reference 2 might be Baker, regardless of which you cited first. The numbers in your text correspond to that alphabetical position.
Name-Year works more like APA style. You write the author’s last name and year in parentheses, such as (Kadonaga 1986), with no comma between them. The reference list is then arranged alphabetically. When a source has two to five authors, you list all of them in the reference list but use only the first author followed by “et al.” in the text. For six or more authors, use the first author plus “et al.” in both places.
One formatting detail that trips people up: in the Name-Year system, the publication year appears right after the author names in the reference list. In Citation-Sequence and Citation-Name, the year moves toward the end of the entry, after the title.
ACS Style for Chemistry
The American Chemical Society (ACS) style is used for chemistry journals and coursework. It supports both superscript numbers and italic numbers in parentheses for in-text citations, depending on the journal. The reference list is numbered in order of appearance, similar to Citation-Sequence.
ACS references follow a distinctive format. For a journal article, you list authors (last name, initials), then the article title, the abbreviated journal name in italics, the year in bold, the volume, issue number in parentheses, and page range. A typical entry looks like this: Hanikel, N.; Pei, X. K.; Chheda, S. et al. Evolution of water structures in metal-organic frameworks for improved atmospheric water harvesting. Science 2021, 374 (6566), 454−459.
ACS also has specific formats for patents, government reports, technical standards, and software, which come up frequently in chemistry research.
AMA and Vancouver for Medicine
Medical papers typically follow either AMA (American Medical Association) style or NLM/Vancouver style. They’re closely related: both use superscript numbers in the text with a numbered reference list.
AMA assigns numbers in order of appearance, and the reference list follows that same order. Vancouver style, developed by the National Library of Medicine, offers the same three systems as CSE (citation-sequence, citation-name, and name-year), giving medical authors more flexibility. The name-year option works like APA but without a comma between the author and year: (Fletcher 2023). One notable difference from APA and AMA is that Vancouver style requires you to cite personal communications in your reference list rather than just mentioning them in the text.
AIP for Physics, IEEE for Engineering
Physics papers follow AIP (American Institute of Physics) style, which uses numbered references in the text. The reference list is ordered by first appearance. AIP formatting is streamlined compared to styles like ACS, reflecting physics journals’ preference for brevity.
Engineering, especially electrical and computer engineering, uses IEEE (Institute of Electrical and Electronics Engineers) style. It also uses bracketed numbers like [1] in the text, with references numbered in order of appearance. If you’re in a field that overlaps physics and engineering, check whether your journal or course follows AIP or IEEE, because the reference list formatting differs even though both are numbered systems.
APA Style in Scientific Contexts
APA (American Psychological Association) style is built for behavioral and social sciences, but it shows up in interdisciplinary scientific work, especially in fields like neuroscience, public health, and environmental psychology. It uses author-date in-text citations, such as (Martinez, 2022), and an alphabetized reference list. If your science course or journal uses APA, you’re most likely in a field that bridges the social and natural sciences.
How to Choose the Right Style
Your choice almost always comes down to two things: your discipline and your audience. If you’re submitting to a journal, check the author guidelines on the journal’s website. They will name the exact style and often link to a template. If you’re writing for a class, your instructor or department will specify a style. When no guidance is given, default to the standard for your field: CSE for biology, ACS for chemistry, AIP for physics, AMA or Vancouver for medicine, IEEE for engineering.
The core difference between these styles is whether they use numbered or author-date citations in the text. Numbered systems (CSE Citation-Sequence, ACS, AMA, AIP, IEEE) are dominant across the sciences because they keep the text cleaner when you’re citing dozens of sources in a single paragraph. Author-date systems (CSE Name-Year, APA) are preferred when the reader benefits from immediately seeing who did the work and when, which matters more in fields where the recency of a finding or the reputation of a research group carries interpretive weight.
Citing Datasets and Software
Scientific citation increasingly includes datasets, code, and analytical tools alongside traditional journal articles. The standard practice is to treat a dataset like any other source: include a formal citation with the creator’s name, a title, the year, and a persistent identifier like a DOI. Many data repositories generate a ready-made citation for each deposit, so you can copy it directly into your reference list.
The FAIR principles (Findable, Accessible, Interoperable, Reusable) guide how scientific data should be shared and cited. A key requirement is that every dataset gets a globally unique, persistent identifier so it can be reliably located and referenced. These principles apply not just to raw data but to the algorithms, tools, and workflows used to produce results. If you used an R package or a Python script to analyze your data, citing it is now expected in many journals.
Citing AI Tools
If you used ChatGPT, Copilot, or another AI tool while preparing a scientific manuscript, most journals now require you to disclose this. The International Committee of Medical Journal Editors (ICMJE) mandates that AI use be clearly described in the manuscript, including the purpose and extent of use. Science journals go further, prohibiting AI-generated content from being cited as a source and requiring authors to report the exact prompt, the tool’s name and version, and where the AI-generated content appears. JAMA has similar requirements, asking for the tool name, version, prompt, and nature of the output in the Acknowledgments or Methods section.
These policies are evolving quickly, so check your target journal’s current author guidelines before submitting. The consistent rule across journals is transparency: if AI contributed to the work, say so explicitly and describe how.