Major title-case systems capitalize the first and last words of a title or subtitle even when the same word would normally be lowercase internally. A converter therefore needs segment endpoints, not only a small-word list.
ReviewedEvidence4 sourcesSectionWriting & Style
Quick answer
Capitalize the first and last word of a title or subtitle. Chicago explicitly illustrates this with “XYZ: What Is It Good For?”, where “For” is capitalized because it is the final word.
Key details
First Wordcapitalize
Last Wordcapitalize regardless of internal small-word rule
Rule Familytitle-boundaries
Further guidance
Converter Logic
This guide marks first/last core tokens for each reviewed segment before applying ordinary internal-word rules, so a final preposition is not incorrectly lowercased.
Endpoint Rule
Chicago explicitly states that the last word in a title is capitalized regardless of syntax. APA and MLA title-case guidance likewise treats title/subtitle endpoints specially.
Subtitle Segments
A colon or other reviewed subtitle boundary creates a new segment whose first and last words must be evaluated as segment endpoints.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
A colon can create a title/subtitle boundary, but nested punctuation still needs structural handling. Chicago capitalizes the first word after a title/subtitle colon; repeated or nested colons should therefore be parsed as boundaries rather than treated as ordinary word punctuation.
Colons, semicolons, and dashes can create capitalization boundaries in titles, while quotation marks and parentheses may introduce embedded structures that require additional analysis. This guide separates punctuation-boundary detection from word-class decisions so it can explain when a new segment begins and when it must leave the result unresolved.
Chicago 18 uses title case for titles of works and changed a long-standing rule: prepositions of five letters or more are now capitalized. Shorter prepositions generally remain lowercase internally, while first and last words are capitalized and “to” remains lowercase as an infinitive marker in ordinary mid-title use.
Apostrophes can mark possession, contractions, or omitted initial letters, and those uses should not be confused with quotation marks. Chicago also has specific title-case examples for initial-apostrophe contractions and for the compound form “O’Clock.”
Hyphens and dashes are not interchangeable in title-case logic. Chicago 18 changed the treatment of later elements in prefix-based hyphenated compounds, while an em dash can act like a parenthetical or subtitle-like boundary depending on structure.
Short words such as “up,” “out,” and “on” can change capitalization when their grammatical role changes. Chicago’s own examples capitalize “Up” or “Out” when those words function adverbially in a phrasal verb, while ordinary prepositional uses can remain lowercase.
The first word of a subtitle is treated as a new capitalization boundary in major title-case systems. APA explicitly capitalizes the first word of a subtitle, Chicago capitalizes the word after a title/subtitle colon, and MLA has published the same treatment in its Style Center guidance.
A title appearing inside another title has its own identity and may need quotation marks, italics, or language-specific treatment. Flattening the inner title into the outer title’s token stream can destroy both formatting and capitalization.
