Most explanations of citation styles just hand you a list of formatting rules to memorise: italicise this, capitalise that. That's not actually the useful part. The useful part is knowing why these styles differ, because that tells you which one your subject actually expects, and why your lecturer keeps correcting the same thing.
APA and Harvard both cite by author and year. MLA cites by author and page number. That single difference explains most of what looks confusing at first.
| Style | Typically used in | In-text example |
|---|---|---|
| APA | Psychology, education, social sciences | (Smith, 2021) |
| Harvard | Business, sciences, most UK general coursework | (Smith, 2021) |
| MLA | Literature, languages, humanities | (Smith 45) |
APA and MLA are both maintained by an actual organisation with an official style manual: the American Psychological Association publishes the APA manual, the Modern Language Association publishes the MLA handbook. Harvard has no equivalent. There is no single "Harvard style" rulebook, and no organisation called Harvard maintains one. It's a loose family of author-date citation conventions that different universities and publishers have each implemented slightly differently.
This is exactly why Harvard referencing feels inconsistent between module handbooks, websites, and reference generators: it genuinely is inconsistent, because there's no single authority defining it. The practical takeaway is simple: when a module asks for "Harvard style," your own department's style guide is the actual authority, not whatever a reference generator produces by default.
MLA citing by page number rather than year reflects what humanities scholarship is usually trying to do: point a reader to the exact passage of a text being discussed, not just which year something was published. A literature essay quoting a specific line from a novel needs the reader to be able to find that line again, which a publication year alone doesn't achieve.
MLA's reference list is also called a "Works Cited" page, not a "Reference list," and it's one of the few style-naming details genuinely worth getting right, since using the wrong label is an easy, visible mistake.
The honest takeaway: these styles aren't arbitrary, each one evolved to suit a different kind of academic argument. Knowing which is which is less about memorising punctuation and more about understanding what your subject actually needs a reader to find.