Every style guide agrees on the basics of title case and disagrees on the details. Here are the rules that actually differ, with examples.
What everyone agrees on
Capitalize:
- the first and last word of the title;
- the first word after a colon (the start of a subtitle);
- nouns, pronouns, verbs, adjectives and adverbs: including short ones such as Is, Be, It, His and So when it’s an adverb.
Lowercase articles (a, an, the) unless they come first or last.
Where they differ: the small words
| Word type | APA 7 | Chicago 18 | AP | MLA 9 |
|---|---|---|---|---|
| Short prepositions (in, of, on, to) | lowercase | lowercase | lowercase | lowercase |
| Long prepositions (about, between, through) | Capitalize (4+ letters) | lowercase | Capitalize (4+ letters) | lowercase |
| Coordinating conjunctions (and, but, or, nor) | lowercase | lowercase | lowercase | lowercase |
| so, yet as conjunctions | lowercase | Capitalize | lowercase | lowercase |
| Subordinating conjunctions (because, if, when) | Capitalize (4+), lowercase if | Capitalize | Capitalize (4+) | Capitalize |
So a single headline can legitimately appear three ways:
- APA/AP: A Walk Through the Woods Between Two Rivers
- Chicago/MLA: A Walk through the Woods between Two Rivers
Hyphenated words
- APA capitalizes both parts of a hyphenated major word: Self-Report, Long-Term.
- Chicago capitalizes the first part and any later parts that aren’t articles, prepositions or coordinating conjunctions: Long-Term, Out-of-Date, E-mail.
- AP capitalizes both parts when both would be capitalized alone.
Tricky cases
“To” in infinitives. All four lowercase it: How to Write a Title.
Phrasal verbs. Up, out, off and on are prepositions in “up the hill” but part of the verb in “Give Up”, “Log In” and “Turn Off”, where Chicago capitalizes them. No automatic converter can always tell the difference (check titles that end in these words).
Acronyms and brand names keep their own capitalization: NASA, iPhone, eBay.
Words after a dash are often capitalized like a subtitle.
Sentence case is gaining ground
Many organizations now use sentence case for headings (GOV.UK, Google’s and Microsoft’s style guides, and APA itself for article and book titles in reference lists). It’s easier to read, faster to apply consistently and avoids the debates above.
A quick decision guide
- Writing an academic paper in APA: title case for your paper title and headings, sentence case for titles in the reference list.
- Writing for a US newspaper: AP rules.
- Publishing a book: Chicago, unless your publisher says otherwise.
- Web and product copy: consider sentence case.
Sources
- Publication Manual of the American Psychological Association (7th ed., 2020), section 6.17.
- The Chicago Manual of Style (18th ed., 2024), chapter 8, “Titles of works”.
- The Associated Press Stylebook, “composition titles”.
- MLA Handbook (9th ed., 2021), “Capitalization of titles”.