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.
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Quick answer
A short particle is not automatically lowercase. In Chicago-style title case, “up” is capitalized when it functions as an adverb, and “out” can be capitalized as part of a phrasal verb such as “Getting Out,” while a true preposition such as “of” remains lowercase. Grammar determines the result.
Chicago Outcapitalize when part of the phrasal verb in the documented example
Chicago Upcapitalize when adverbial
Rule Familyphrasal-verbs
Important caveats
Converter Boundary
This is a principal blocker for the Chicago converter because a browser-only word list cannot safely infer every part of speech from spelling alone.
Further guidance
Out Example
Chicago revised its own analysis of “Getting Out of Saigon”: “out” is better treated as part of the phrasal verb “getting out” and capitalized, while “of” remains a preposition.
Part Of Speech Rule
The same spelling can be a preposition, adverb, particle, adjective, or another category in different constructions. Surface word length alone is not enough for reliable automation.
Up Example
Chicago explains that “up” in “It’s Up to You” is an adverb and is therefore capitalized under its title-case rules.
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.
Prepositions are one of the clearest places where title styles diverge. APA uses a four-letter major-word threshold, Chicago 18 capitalizes prepositions of five letters or more, and MLA editorial guidance generally lowercases internal prepositions regardless of length.
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.
“Off” cannot be assigned one safe capitalization from spelling alone. As a short preposition it is normally lowercase internally in APA and Chicago, but as an adverb or verb particle it is a major word and is capitalized; the surrounding phrase determines the answer.
“To” is normally lowercase in the middle of titles under APA, Chicago, and MLA-style capitalization when it functions as a short preposition; Chicago also explicitly keeps “to” lowercase as an infinitive marker in ordinary mid-title position. Edge position can change the result.
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.
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.”
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.
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.
