APA Style (7th edition), the standard for psychology, education, and many social sciences, has a distinctive quirk: it uses different capitalization rules depending on where a title appears.

In the body of your paper — when referring to a source title in your text — APA uses title case: capitalize all major words (nouns, verbs, adjectives, adverbs, pronouns) and all words of four or more letters. 'In *The Structure of Scientific Revolutions*, Kuhn argues...' Here the book title is in title case.

In the reference list — the bibliography entries at the end of your paper — APA uses sentence case: capitalize only the first word of the title, the first word of any subtitle (after a colon), and proper nouns. 'Kuhn, T. S. (1962). The structure of scientific revolutions. University of Chicago Press.' Here only 'The' and no other word is capitalized (structure, scientific, revolutions are all lowercase).

This dual system trips up more students than any other APA rule. The mnemonic: title case in the text you write, sentence case in the reference list entries.

• ▸In-text: 'Attention Is All You Need introduced the transformer architecture.'
• ▸Reference list: 'Vaswani, A., et al. (2017). Attention is all you need.'

MLA Style (9th edition), the standard for literature, languages, and humanities, uses title case consistently everywhere a title appears — in the text and in the Works Cited list.

MLA's specific rule for title case: capitalize the first word, the last word, and all principal words — nouns, pronouns, verbs, adjectives, adverbs, and subordinating conjunctions. Lowercase articles (a, an, the), coordinating conjunctions (and, but, or, nor, for, so, yet), and prepositions, regardless of length, unless they are the first or last word.

• ▸'The Great Gatsby' — 'The' capitalized as the first word
• ▸'A Room of One's Own' — all words capitalized; 'of' stays lowercase
• ▸'War and Peace' — 'and' stays lowercase as a coordinating conjunction
• ▸'Between the World and Me' — 'the' and 'and' lowercase; 'Between' and 'World' and 'Me' capitalized

MLA differs from AP Style specifically on longer prepositions — MLA lowercases all prepositions regardless of length ('Throughout', 'Beneath', 'Within' would all be lowercase mid-title), whereas AP capitalizes prepositions of four or more letters. This is a common source of confusion for students who learned AP-style capitalization in journalism classes.

The Chicago Manual of Style, widely used in history, publishing, and some social sciences, offers writers a choice between two capitalization systems — but requires consistency once you pick one.

Headline-style capitalization (the traditional Chicago approach and the more common choice): capitalize the first and last words of a title and all major words in between. This is essentially the same principle as MLA and traditional English title case — lowercase articles, coordinating conjunctions, and prepositions (regardless of length) unless they begin or end the title.

Sentence-style capitalization (an increasingly used alternative, especially in scientific and technical Chicago-style writing): capitalize only the first word of the title and subtitle, and any proper nouns — identical in principle to APA's reference-list style.

Chicago explicitly states that both systems are acceptable, but the chosen system must be applied consistently throughout an entire document or publication. Academic journals using Chicago style typically specify which system they require in their author guidelines — always check rather than assume.

Section headings within the body of an academic paper (Introduction, Methods, Discussion, etc.) follow their own conventions, distinct from title capitalization rules.

APA (7th edition) specifies five heading levels, each with its own formatting, but the capitalization rule for all of them is consistent: use title case for headings. 'Materials and Methods', 'Results and Discussion' — all major words capitalized.

MLA does not mandate a specific heading system the way APA does, since MLA papers are typically shorter and use fewer internal headings. When headings are used, title case is the conventional choice.

Chicago-style papers often use headline-style capitalization for headings even when the document body uses sentence-style capitalization for titles in citations — headings and citation titles are treated as separate style decisions.

A frequent point of confusion in academic writing: should the name of a theory, model, or academic discipline be capitalized?

Academic disciplines are lowercase when used generically: 'she studies psychology', 'the field of sociology'. They are capitalized only when part of an official department or degree name: 'the Department of Psychology', 'a Bachelor of Arts in Sociology'.

Named theories and models follow proper-noun rules only when they include a proper noun (typically the originator's name): 'Freudian theory', 'Darwinian evolution', 'Maslow's hierarchy of needs' (Maslow capitalized, hierarchy of needs lowercase). Generic theory names without a proper noun stay lowercase: 'social learning theory', 'cognitive dissonance', 'attachment theory'.

This rule trips up writers because capitalizing a theory name can feel like it adds authority or formality — but APA, MLA, and Chicago all agree: capitalize only the proper noun portion, not the whole term.