Citation Styles: APA, MLA, Chicago, and How to Choose the Right One

What Is a Citation Style?

A citation style is a rulebook for crediting your sources. It tells you two things: how to reference a source within your text (called an in-text citation), and how to list all your sources at the end of the paper (called a reference list, bibliography, or works cited page, depending on the style).

Why are there so many different styles? Different academic disciplines developed their own conventions because they have different priorities. Scientists care most about when something was published (so author and date come first). Humanities scholars care more about which page or edition you're drawing from. Engineers need a clean, numeric system that doesn't interrupt the technical reading flow.

The result is a system where your field essentially tells you which "rulebook" to follow. Once you know the rules for your style, the rest is just execution.

"A citation style is a set of rules that tells you exactly how to credit your sources, and every academic field has its own preferred format."

Which Citation Style Do You Need? (Start Here)

Before you read anything else, answer this question: what subject is your paper for?

That one question answers 90% of citation style decisions. Here's a quick reference table:

The second rule: your professor's instructions always override discipline convention. If your syllabus specifies a style, use that, even if it's not the typical one for your field. When in doubt, ask. A quick email to your professor before you start is a lot easier than reformatting 30 references after you're done.

"When in doubt, check your syllabus, your professor's instructions always override discipline convention."

The 5 Most Common Citation Styles

Most students will only ever encounter a handful of citation styles throughout their academic career. Here are the five you're most likely to need.

APA (American Psychological Association)

APA is the standard in social sciences, psychology, and education. It uses an author-date system for in-text citations, so a reference inside your text looks like this: (Smith, 2020). At the end of the paper, you include a reference list organized alphabetically by author's last name.

Quick format example (journal article): Smith, J. A. (2020). The effects of study habits on academic performance. Journal of Educational Psychology, 45(3), 112–128.

For a full breakdown of every APA element, see our APA format guide.

MLA (Modern Language Association)

MLA is used mainly in the humanities — literature, language studies, and cultural analysis. Instead of author-date, MLA uses author-page in-text citations: (Smith 45). Your source list at the end is called a Works Cited page.

Quick format example: Smith, John A. "Academic Writing in the Digital Age." Journal of Humanities, vol. 12, no. 3, 2020, pp. 44–60.

If you're deciding between these two, our APA vs MLA format comparison breaks down exactly when to use each.

Chicago / Turabian

Chicago style is standard in history and some humanities fields. It comes in two versions: Notes-Bibliography (common in history, using footnotes) and Author-Date (similar to APA). Turabian is essentially a simplified version of Chicago designed for students.

Quick format example (Notes-Bibliography): John A. Smith, The History of Academic Writing (New York: Academic Press, 2020), 45.

IEEE

IEEE (Institute of Electrical and Electronics Engineers) is the standard in engineering, computer science, and technical disciplines. It uses a numeric system, you assign a number to each source and use that number in brackets throughout the text: [1]. Your reference list is numbered in the order sources appear.

Quick format example: [1] J. A. Smith, "Neural network optimization," IEEE Transactions on Neural Networks, vol. 31, no. 4, pp. 1200–1215, 2020.

Harvard

Harvard referencing is widely used in economics, some humanities, and sciences, particularly in UK and Australian universities. It's similar to APA in that it uses an author-date in-text format, but with minor formatting differences. There's no single official publisher for Harvard style, so specific rules can vary by institution.

Quick format example: Smith, J.A. (2020) Research Methods in Economics. London: Academic Press.

Other Citation Styles (Quick Reference)

You probably won't need these unless you're in a specific field, but here's a quick reference for the less common styles:

ASA (American Sociological Association): Used in sociology. Author-date in-text citations, similar to APA but with some formatting differences in the reference list.

OSCOLA (Oxford Standard for Citation of Legal Authorities): The standard for UK law schools. Uses footnotes for citations rather than in-text references.

AMA (American Medical Association): Used in medicine and health sciences. Numeric in-text citations (superscript numbers), ordered reference list.

ACS (American Chemical Society): Used in chemistry. Supports multiple citation formats including numeric and author-date.

NLM (National Library of Medicine): Used in biomedical and health sciences. Numeric citations, widely used in clinical research.

AAA (American Anthropological Association): Used in anthropology. Author-date format with specific rules for field-specific sources.

APSA (American Political Science Association): Used in political science. Author-date or footnote style depending on the publication.

The Three Types of In-Text Citations

All citation styles fall into one of three categories based on how they handle in-text references. Understanding these three types makes it much easier to switch between styles.

Parenthetical (author-date or author-page): The source information appears directly in the text inside parentheses. APA uses author-date: (Smith, 2020). MLA uses author-page: (Smith 45). Harvard also uses author-date. This is the most common type.

Note style (footnotes or endnotes): Instead of in-text references, you place a superscript number in your text and put the citation at the bottom of the page (footnote) or end of the document (endnote). Chicago Notes-Bibliography and OSCOLA use this system.

Numeric: You assign a number to each source and use that number in brackets or superscript throughout the text. IEEE, AMA, ACS, and NLM all use numeric systems.

"The three types of in-text citations are parenthetical, note-based, and numeric, and which one you use depends entirely on your citation style."

For a complete breakdown of how APA handles in-text references specifically, see our guide to APA in-text citations.

What's the Easiest Citation Style?

For most students starting out, MLA is considered the easiest. It has fewer formatting requirements than APA (no title page, simpler reference structure), and the in-text citation is just author and page number. If your professor gives you a choice and you're new to academic writing, MLA is a solid starting point.

That said, APA is worth learning even if it's a bit more involved, because it's the standard in many U.S. degree programs, especially if you're in the social sciences, education, or any health-related field. Knowing APA will serve you well throughout your academic career.

Chicago Notes-Bibliography is the most complex of the common styles because of the footnote system and the two separate versions. It's usually reserved for upper-level courses and graduate work in history or humanities.

"For most students starting out, MLA requires the fewest formatting decisions, but APA is worth learning since it's the standard in many U.S. degree programs."

Tips for Getting Your Citations Right

Getting your citations right isn't just about following rules,  it protects you from plagiarism accusations and shows your professor you've done actual research. Here's what makes the biggest difference:

Track your sources as you go. 

Don't wait until you've finished writing to build your reference list. Every time you use a source, note down all the details you'll need: author, title, publication, date, page numbers. Reconstructing this information later is tedious and error-prone.

Paraphrase properly, and still cite. 

Putting something in your own words doesn't mean you don't have to cite it. If the idea came from someone else, credit them. Paraphrasing without citation is still plagiarism.

Double-check format accuracy. 

Citation tools like Zotero, Citation Machine, or your library's resources are useful starting points, but they make mistakes. 

Follow your institution's guide first. 

Many universities publish their own citation style guides or preferred variations. Check your library's website, your school's version always takes priority over what you find on a general website.

Ask when you're unsure. 

If the syllabus doesn't specify, a quick email to your professor before you start will save you from reformatting everything at the end.

Conclusion

Understanding citation styles is an essential part of academic writing. Proper citations not only give credit to original authors but also strengthen the credibility and reliability of your research. By learning the differences between major citation styles and knowing when to use them, students can present their work more professionally and avoid issues such as plagiarism.

However, mastering citation rules and formatting can sometimes be confusing, especially when working under tight deadlines. If you need help organizing your references or formatting your paper correctly, professional support can make the process much easier.

Our experienced writers can assist you with properly formatted academic papers, including accurate citations and references in the required style.