The main citation styles for essays are APA, MLA, Chicago and Harvard. Each records the same information about a source, but in a different order, with different punctuation and a different in-text format.
This guide compares the four styles side by side, shows one source cited in each, and gives you a simple route to the right choice when your assignment is not clear.
Which Citation Style Fits Your Essay
- APA 7th: psychology, education, nursing, business and most social sciences.
- MLA 9th: English literature, languages, composition and many humanities courses.
- Chicago: history and some arts subjects, usually with footnotes.
- Harvard: widely taught at UK and Australian universities across many subjects.
Your assignment brief or module handbook always outranks this list. If it names a style, use that one.
The Four Styles at a Glance
Citation styles grew up inside different academic fields, and each reflects what that field values most. The differences are not arbitrary once you see the reasoning.
- APA puts the date first because social science research ages quickly, and readers want to know how recent a finding is.
- MLA puts the page first because literary scholars quote and analyze specific passages.
- Chicago notes keep the text clean because historians cite many archival and primary sources and often add commentary in the notes.
- Harvard is a general author-date system used across disciplines, with versions that vary slightly between universities.
Side-by-Side Comparison
| Feature | APA 7th | MLA 9th | Chicago notes | Harvard |
|---|---|---|---|---|
| In-text format | (Author, year) | (Author page) | Superscript note number | (Author, year) |
| Page in citation | Required for quotes | Included whenever available | In the note | Required for quotes |
| List title | References | Works Cited | Bibliography | Reference list |
| Article titles | Sentence case, no quotation marks | Title case in quotation marks | Title case in quotation marks | Usually sentence case in single quotation marks |
| Typical subjects | Social sciences, nursing, business | Literature, languages | History, arts | Many subjects in the UK and Australia |
One Source Cited in Each Style
The clearest way to see the differences is to cite one journal article in all four styles. The source here is an illustrative article by two authors.
APA 7th reference: Lopez, M., & Chen, D. (2023). Sleep quality and academic performance in first-year students. Journal of Student Wellbeing, 12(3), 45–60. https://doi.org/10.1234/jsw.2023.0045
APA in text: (Lopez & Chen, 2023) or, for a quotation, (Lopez & Chen, 2023, p. 47)
MLA 9th Works Cited entry: Lopez, Maria, and David Chen. "Sleep Quality and Academic Performance in First-Year Students." Journal of Student Wellbeing, vol. 12, no. 3, 2023, pp. 45–60, https://doi.org/10.1234/jsw.2023.0045.
MLA in text: (Lopez and Chen 47)
Chicago note: 1. Maria Lopez and David Chen, "Sleep Quality and Academic Performance in First-Year Students," Journal of Student Wellbeing 12, no. 3 (2023): 47, https://doi.org/10.1234/jsw.2023.0045.
Chicago bibliography: Lopez, Maria, and David Chen. "Sleep Quality and Academic Performance in First-Year Students." Journal of Student Wellbeing 12, no. 3 (2023): 45–60. https://doi.org/10.1234/jsw.2023.0045.
Harvard reference: Lopez, M. and Chen, D. (2023) 'Sleep quality and academic performance in first-year students', Journal of Student Wellbeing, 12(3), pp. 45–60. Available at: https://doi.org/10.1234/jsw.2023.0045.
Harvard in text: (Lopez and Chen, 2023, p. 47)
Look at the small details: APA uses an ampersand and initials, MLA writes full first names and "and", and Chicago changes the order of names between note and bibliography.
How the Two Halves Work Together
Every style has two halves that must match. The in-text citation points to a source briefly, and the full entry in your list gives the reader everything needed to find it.
In author-date styles, the reader matches the surname and year. In MLA, the surname leads to the Works Cited entry. In numbered styles, the number leads to the matching entry. Whichever style you use, each in-text citation needs a list entry and each list entry needs at least one citation in the text.
APA: The Social Sciences Default
APA 7th is the most common style for essays in psychology, education, nursing, health and business. Its author-date citations let readers judge at a glance how current your evidence is.
Key habits to remember: use "et al." in text from the first citation when a source has three or more authors, list up to 20 authors in the reference, and format article titles in sentence case without quotation marks.
MLA: The Humanities Default
MLA 9th suits essays that analyze texts closely. The in-text citation gives the author and page with no comma between them, so readers can find the exact passage you discuss.
MLA builds every entry from "core elements" in a set order: author, title of source, title of container, other contributors, version, number, publisher, publication date and location. Once you understand that order, you can cite almost any source.
Chicago: Notes or Author-Date
Chicago has two systems. Notes and bibliography is common in history and the arts: each citation is a numbered footnote, and a bibliography lists every source at the end.
Chicago author-date works much like APA, with (Author year, page) in the text and a reference list. Check which system your tutor wants, because the two are not interchangeable within one essay.
Harvard: One Name, Several Versions
Harvard is not controlled by a single official manual. Universities publish their own Harvard guides, and small details such as punctuation, italics and the "Available at" wording can differ between them.
If your course uses Harvard, follow your university library's guide exactly. Consistency with that guide matters more than matching any other version you find online.
Other Styles You May Meet
Some subjects use specialized styles instead of the big four. If your course is in one of these fields, expect to see them named in your brief.
| Style | Main subjects | In-text format | List order |
|---|---|---|---|
| IEEE | Engineering, computing | Number in square brackets, such as [1] | Numerical, in order of first citation |
| Vancouver | Medicine, health sciences | Number in brackets or superscript | Numerical, in order of first citation |
| AMA 11th | Medicine, some nursing courses | Superscript number | Numerical, in order of first citation |
| OSCOLA | Law in the UK | Footnotes | Bibliography and tables of cases and legislation, where required |
| MHRA | Modern languages, some humanities | Footnotes | Alphabetical bibliography |
Numbered styles reuse the same number every time you cite a source again. That makes them compact, but it also means adding a new source early in a draft can change every number after it, so add citations carefully.
How to Choose When the Brief Is Unclear
- Read the assignment brief and rubric for a named style.
- Check the module handbook or course page for a department default.
- Look at the style used in your set readings and earlier marked work.
- Ask your tutor directly. A short email is better than a guess.
- If there is truly no guidance, use APA for social science and business essays or MLA for literature and language essays, and apply it consistently.
Common Style Mistakes
| Mistake | Fix |
|---|---|
| Mixing styles, such as APA references with MLA in-text citations | Pick one style and apply it everywhere |
| Using an older edition, such as APA 6th rules | Check your work against the current edition |
| Copying generator output without checking | Compare each entry with a trusted guide for capitals, italics and DOIs |
| Missing page numbers for quotations | Add the page or paragraph number to every direct quote |
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Frequently Asked Questions
APA, MLA, Chicago and Harvard cover most university essays. Some subjects use specialized styles such as IEEE for engineering, Vancouver for medicine or OSCOLA for law.
None is truly easier. APA, MLA and Harvard avoid footnotes, which many students find simpler than Chicago notes.
Ask your tutor first. If there is no guidance, choose the style common in your subject and apply it consistently.
Both use author-date citations. They differ in details such as the ampersand, article title formatting, italics and how online sources are introduced.
Turabian is a student version of Chicago with the same two systems, adapted for papers and theses rather than published books.
In APA, MLA and Chicago, yes, the list starts on a new page at the end of the essay. Many Harvard guides follow the same practice.
APA 7th asks for a DOI whenever one exists, formatted as a link. MLA and Chicago recommend including one when available.
No. Use a single style throughout unless your tutor gives specific instructions otherwise.
Most nursing programs use APA 7th. A few medical and health courses use Vancouver or AMA, so check your program handbook.