Which Words Do You Capitalise in a Title?

You have a title. Something like a study of the relationship between sleep and memory. Which words get a capital?

Ask three style guides and you get three answers. Ask a generic title case converter and you get a fourth, which matches none of them. That is not a small annoyance — it is the reason people lose marks on a bibliography they spent an hour formatting.

Here is what each style actually requires.

The three rules, stated plainly

APA 7 uses a length rule. Capitalise every word of four letters or more, whatever its part of speech, plus the first word, the last word, and the first word after a colon. Everything shorter than four letters is capitalised too if it is a major word — a noun, verb, adjective, adverb or pronoun.

The consequence people miss: APA capitalises prepositions once they are four letters long. "Between", "With", "From", "Through", "Against", "About" all take a capital in APA.

MLA 9 uses a part-of-speech rule. Capitalise nouns, verbs, adjectives, adverbs and pronouns. Leave lowercase: articles (a, an, the), prepositions of any length, and coordinating conjunctions (and, but, or, nor, for, so, yet) — unless one of them is the first or last word.

So MLA gives "between", "with" and "from" in lowercase, however long they are.

Chicago 17 works like MLA, with two additions. It also lowercases as. And in a hyphenated compound it capitalises both halves.

Run our example through all three:

• APA 7 — A Study of the Relationship Between Sleep and Memory
• MLA 9 — A Study of the Relationship between Sleep and Memory
• Chicago 17 — A Study of the Relationship between Sleep and Memory

All three are correct. Only one is correct for your assignment.

Why they differ, which makes it easier to remember

APA's rule is mechanical on purpose. A reference list has hundreds of entries and several authors, and "count the letters" can be applied identically by everybody, at speed, without anyone needing to agree on whether a word is functioning as a preposition. Consistency across a large document was the design goal, and a slightly odd-looking "Evidence From Trials" is the price.

MLA and Chicago optimise for how the title reads. Prepositions are structural glue; capitalising them makes a title look lumpy. Their rule produces better-looking titles and requires the writer to know some grammar. That is a real trade, made deliberately, in opposite directions.

Once you know which problem each style was solving, you rarely have to look the rules up again.

The four traps

1. The first word after a colon. All three styles capitalise it, whatever it is. The Silent Problem: A Study of Office Hours. This is the single most common error in generic converters, which treat the subtitle as a continuation of the sentence and lowercase "a".

2. The last word. Always capitalised, in every style, however minor. The Things We Do Not Talk About. "About" is a preposition and it still gets a capital, because it is last.

3. Hyphenated compounds. Capitalise both halves when both are major words: Twentieth-Century Prose, A Well-Made Play. APA and MLA leave a minor second half alone, giving forms like Follow-up; Chicago capitalises the second half regardless.

4. APA's title case is not APA's reference list. This one costs marks quietly. APA uses title case for journal names and for headings, but sentence case for the titles of articles, chapters and books inside the reference list. So the article is A study of the relationship between sleep and memory while the journal it appeared in is Journal of Sleep Research. Both appear in the same entry, cased differently, on purpose.

If you take one thing from this post, take that one. It is the difference that most often survives all the way to a marked bibliography.

The words nobody can decide for you

A few words change capitalisation depending on what they are doing in the sentence, and no tool without a grammatical parse can resolve them.

Up is an adverb in Look Up the Answer — capitalised. It is a preposition in Notes up the Coast — lowercase. Same word, same style guide, different answer, and the only thing that distinguishes them is meaning.

The same goes for on, in, out, over, down, through, by, past and near. Every style capitalises the adverb and lowercases the preposition, so every one of these is genuinely ambiguous out of context.

Any converter that silently picks one is wrong roughly half the time on those words. Our Title Case Converter flags them instead and shows you both readings, so you can make the call yourself. It handles the four traps above automatically, and gives you sentence case alongside the title case — because if you are formatting an APA reference you almost certainly need both.

A worked example

Take: coping with stress from social media: a longitudinal study of first-year students

APA 7 Coping With Stress From Social Media: A Longitudinal Study of First-Year Students

With and From are four letters, so they take capitals. of is two, so it does not. A is capitalised because it opens the subtitle.

MLA 9 Coping with Stress from Social Media: A Longitudinal Study of First-Year Students

with and from are prepositions, so they stay lowercase whatever their length.

Chicago 17 Coping with Stress from Social Media: A Longitudinal Study of First-Year Students

Identical to MLA here — the differences between the two only surface with as or with certain hyphenated forms.

And in an APA reference list, that same article title would appear as: Coping with stress from social media: A longitudinal study of first-year students

If you are not sure which style you are in

Check the assignment brief first, then the module handbook, then ask. Do not infer it from what your classmates are doing.

If you want the longer version of what separates the three — why author names, dates and in-text citations differ as well — we wrote that up in APA vs MLA vs Chicago. And if you are assembling the references themselves rather than just casing them, the Citation Generator builds them from publisher records in all six major styles, which removes a different category of error entirely.