Hyphenated compounds cannot be capitalized safely with one universal “capitalize everything after a hyphen” rule. APA explicitly capitalizes the second part of hyphenated major words, while Chicago 18 changed its prefix-compound treatment and still applies grammatical title-case rules to individual elements.
ReviewedEvidence2 sourcesSectionWriting & Style
Quick answer
Treat each style separately. APA 7 capitalizes the second part of a hyphenated major word such as “Self-Report.” Chicago 18 now capitalizes a second element after a prefix according to the general title-case rule, so forms such as “Anti-Intellectual” differ from older Chicago treatment. Do not assume every hyphenated element is automatically capitalized.
Key details
APA 7capitalize the second part of a hyphenated major word
Chicago 18apply general title-case rules to later elements; prefix-compound treatment changed in the 18th edition
Converter Statusresearched rule family; named modes still gated
Rule Familycompounds
Style-by-style guidance
APA 7
APA title case explicitly includes the second part of hyphenated major words among the elements that receive capitalization. Minor elements still depend on APA’s major/minor-word rules.
Chicago 18
Chicago 18 changed the treatment of hyphenated terms that begin with prefixes: subsequent elements are now capitalized according to the general title-capitalization rule.
Important caveats
Current Engine Boundary
The named style converters require manual review until the compound classifier and regression cases distinguish prefix compounds from other hyphenated structures.
Why Automation Is Hard
Hyphens join many different structures: prefixes, compound adjectives, spelled-out numbers, and multiword phrases. A safe converter therefore needs element-level rules and cannot simply capitalize every segment.
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.
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.
APA title case capitalizes the first word, the first word of a subtitle, major words, and words of four letters or more while keeping short minor words lowercase in ordinary mid-title positions.
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.
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.
Chicago 18 changed how later elements in prefix-based hyphenated compounds are capitalized: each component now follows the general title-case rule. Safe automatic treatment still requires recognizing that the hyphen truly joins a reviewed prefix compound.
Multiword prepositions such as “according to,” “because of,” “instead of,” “out of,” and “up to” should not be handled by a single crude small-word list. Different style systems analyze components differently, and some phrases contain words that can change grammatical role.
Part of speech can change title capitalization for surface-identical words such as “than,” “like,” “over,” “off,” and phrasal particles. A reliable converter therefore needs reviewed grammatical context instead of a single lowercase-word list.
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.
