If you have ever stared at an assignment that says “use the correct citation style” and felt unsure where to begin, you are not alone. This guide explains the major citation styles (APA, MLA, Chicago, Harvard, and IEEE), shows a correct example of each, and helps you decide which one fits your subject and your instructor’s rules.
What citation styles are and why they differ
A citation style is an agreed set of rules for crediting the sources you used. The rules cover two things: the full reference (in a list at the end of your paper) and the in-text marker that points to it. Different academic fields developed different citation styles because they value different details.
For example, the humanities often care about the exact page where a quotation appears, while the sciences care most about when research was published. That is why some styles put the year right after the author and others tuck it near the end. If you are new to the idea, our overview of what a citation is is a good first stop.
The five most common citation styles
APA (7th edition): social sciences
APA style comes from the American Psychological Association. It is the standard in psychology, education, nursing, business, and most social sciences. APA uses an author-date system, so the publication year sits near the front. Note the ampersand (&) between authors in the reference list and the parentheses.
Smith, J. A., & Brown, L. M. (2021). Understanding research methods in education (2nd ed.). Academic Press.
In-text: (Smith & Brown, 2021)
For a full walkthrough, see our APA format guide, or build an entry instantly with the APA citation generator.
MLA (9th edition): humanities
MLA style comes from the Modern Language Association and is used in literature, languages, philosophy, and the arts. The reference list is called the Works Cited page. MLA spells out “and” between two authors and uses an author-page in-text citation with no comma and no “p.” before the number.
Smith, John, and Laura Brown. Understanding Research Methods in Literature. 2nd ed., Academic Press, 2021.
In-text: (Smith and Brown 45)
The MLA format guide covers the details, and the MLA citation generator formats your sources for you. If you are choosing between these two, our comparison of APA vs MLA may help.
Chicago (17th/18th edition): history and publishing
The Chicago Manual of Style offers two systems. Notes-Bibliography (used in history, art history, and the humanities) places sources in footnotes and a bibliography. Author-Date (used in many sciences and social sciences) works like APA. The 18th edition (2024) is now current, though many courses still use the 17th, and the basic forms below are the same in both. Here is the Notes-Bibliography form.
Smith, John, and Laura Brown. Understanding Research Methods in History. 2nd ed. Chicago: Academic Press, 2021.
First footnote: John Smith and Laura Brown, Understanding Research Methods in History, 2nd ed. (Chicago: Academic Press, 2021), 45.
For the Author-Date variant and more, read the Chicago style guide or use the Chicago citation generator. Students using Turabian, a version of Chicago made for coursework, can use the Turabian citation generator.
Harvard: business and the sciences (especially UK and Australia)
Harvard is an author-date style rather than a single published manual, so small details vary between universities. Always check your institution’s version. It is widely used in business, economics, and the sciences, especially at UK and Australian universities. A common form looks like this.
Smith, J. and Brown, L. (2021) Understanding research methods in business. 2nd edn. London: Academic Press.
In-text: (Smith and Brown, 2021, p. 45)
Our Harvard referencing guide explains the variations, and the Harvard citation generator handles the formatting.
IEEE: engineering and computer science
IEEE style, from the Institute of Electrical and Electronics Engineers, is standard in engineering, computer science, and information technology. Instead of author names, it uses numbered references in square brackets. The numbers match a list ordered by first appearance in the text, not alphabetically. Note that author first names are abbreviated to initials placed before the surname.
[1] J. A. Smith and L. M. Brown, Understanding Research Methods in Engineering, 2nd ed. New York, NY, USA: Academic Press, 2021.
In-text: As shown in [1], the method is reliable.
The IEEE citation generator numbers and formats your sources automatically.
Which citation style should you use?
The single most reliable rule is this: use the style your instructor, department, or journal requires. If a syllabus or submission guideline names a style, that decision is already made. When no style is specified, your discipline is the best guide.
- Psychology, education, nursing, business, social sciences: APA
- Literature, languages, philosophy, the arts: MLA
- History, art history, and book publishing: Chicago (often Notes-Bibliography)
- Business and sciences, especially in the UK and Australia: Harvard
- Engineering, computer science, and IT: IEEE
Other fields use their own styles. Medicine often uses AMA or Vancouver, chemistry uses ACS, biology uses CSE, sociology uses ASA, and law uses Bluebook. You can format these with the AMA citation generator or the Vancouver citation generator if your course calls for them.
How the styles differ at a glance
Knowing a few key contrasts makes it easier to spot which style a document uses and to switch between them.
- In-text marker: APA and Harvard use author-date, MLA uses author-page, Chicago Notes-Bibliography uses footnotes, and IEEE uses a bracketed number.
- Reference list name: APA calls it References, MLA calls it Works Cited, Chicago and Harvard call it a Bibliography or Reference list, and IEEE calls it References.
- Joining authors: APA uses an ampersand (&) in the reference list, while MLA, Chicago, and Harvard spell out “and”.
- List order: APA, MLA, Chicago, and Harvard list sources alphabetically; IEEE lists them in citation order.
If the difference between References, Works Cited, and Bibliography is still fuzzy, our explainer on works cited vs bibliography vs references clears it up. To understand the marker inside your text, see our guide to in-text citations.
Tips for getting citations right
- Confirm the required style before you start writing, not the night before the deadline.
- Use the current edition: APA 7th, MLA 9th, and Chicago 18th (the 17th is still widely accepted) are the standards in 2026.
- Be consistent. Do not mix two styles in one paper.
- Record source details (author, title, year, publisher, page numbers, URL) as you research, so you do not have to hunt for them later.
- Check small details like italics, capitalization, and punctuation, because these are where most marks are lost.
Careful citing is also the simplest way to avoid plagiarism. Whatever style you land on, you can paste your source details into our free citation generator and get a formatted entry in seconds.
Frequently asked questions
Can I choose my own citation style?
Usually no. If your instructor, department, or journal requires a specific style, you must use it. Only when no style is specified should you pick one, and then you should match the style most common in your discipline and use it consistently.
Are APA and Harvard the same thing?
They are similar but not identical. Both are author-date styles, so the in-text citations look alike. However, APA is a single published standard (currently the 7th edition), while Harvard is a general approach with small differences between universities. APA uses an ampersand in the reference list, and many Harvard versions spell out “and”.
Which citation style is the easiest to use?
There is no single easiest style, but author-date styles like APA and Harvard feel straightforward to many students because the in-text citation is short and consistent. The best choice is still the one your assignment requires, since using the correct style matters more than using a familiar one.
Do I need to learn every citation style?
No. Most students mainly use the one or two styles common in their field. It helps to recognize the differences, but you only need to apply the style required for each assignment. A citation generator can format any of these styles for you, so you do not have to memorize every rule.