Sentence Case vs Title Case
Two capitalisation systems for titles — and the citation styles that require each.
Title case (headline style) capitalises the first and last words plus all principal words: The Old Man and the Sea. Sentence case capitalises only the first word, the first word after a colon, and proper nouns: The old man and the sea.
Style regimes diverge sharply. Chicago and MLA use title case for titles of works; APA uses sentence case in reference-list entries but title case for the journal name; most scientific publishers use sentence case throughout. The choice is not aesthetic — a reference list that mixes both signals careless citation work.
The hard part of title case is the small words. Articles, coordinating conjunctions, and prepositions stay lowercase unless they are first, last, or (in Chicago) used adverbially, which is why 'Look Up' capitalises 'Up' but 'A Room with a View' does not capitalise 'with'.
Common mistake: applying title case to a quoted sentence. Quoted running text keeps its original sentence capitalisation; only titles take title case.
“Kahneman, D. (2011). Thinking, fast and slow. Farrar, Straus and Giroux.”
Keep reading the glossary
The set of conventions governing when to keep, change, or silently bracket the first letter of a quoted passage.
How to punctuate a short work's title, including what happens when it meets other punctuation.
The list of works cited or consulted, printed at the end of a book, chapter, or article.
A formal reference that lets a reader locate the source of a quote.