“As” is a grammar-sensitive title-case word. APA normally lowercases it internally because it is a short conjunction or preposition, while Chicago 18 explicitly keeps “as” lowercase in any grammatical function except where a boundary rule independently requires capitalization.
ReviewedEvidence2 sourcesSectionWriting & Style
Quick answer
Usually lowercase “as” in the middle in APA and Chicago title case. APA treats short conjunctions/prepositions as minor words; Chicago 18 goes further and explicitly keeps “as” lowercase in any grammatical function. Capitalize it when it begins a title or subtitle, and apply the required style’s boundary rules.
Key details
APA 7normally lowercase internally as a short conjunction/preposition
Automation Classlexical override available for Chicago 18
Chicago 18lowercase internally in any grammatical function
Wordas
Word Classcontext-sensitive function word
Style-by-style guidance
APA 7
APA title case normally lowercases short conjunctions and short prepositions in internal positions, so “as” is ordinarily lowercase there.
Chicago 18
Chicago’s current guidance explicitly says “as” remains lowercase in any grammatical function, which avoids having to distinguish its conjunction, adverb, and preposition-like uses for ordinary internal title positions.
Important caveats
Automation Note
“As” is unusually friendly to Chicago automation because Chicago supplies a lexical exception. APA still belongs to a broader part-of-speech/minor-word system rather than a universal word list.
Boundary Rule
First-word and subtitle-boundary rules can still require an initial capital. A word-level rule does not override a title-position rule.
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.
“For” is normally lowercase in the middle of both APA and Chicago title case when it functions as a short conjunction or short preposition. Position still matters, and a converter should not generalize that answer to unrelated grammatical uses without checking context.
“Than” exposes a genuine style-engine edge case. APA capitalizes it because it has four letters, while Chicago 18 may lowercase it as a preposition but capitalize it as a conjunction, so Chicago output can depend on the grammatical structure of the title.
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.
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.
Coordinating conjunctions are a major source of title-case differences: APA lowercases short conjunctions, while current Chicago names a narrower lowercase set and capitalizes “so” and “yet.”
APA capitalizes “About” internally because it has at least four letters. Chicago 18 also capitalizes it when used as a preposition because current Chicago capitalizes prepositions of five letters or more. MLA treatment still depends on grammatical function, so prepositional and principal-word uses should not be collapsed into one rule.
APA capitalizes “Across” internally because it has at least four letters. Chicago 18 also capitalizes it when used as a preposition because current Chicago capitalizes prepositions of five letters or more. MLA treatment still depends on grammatical function, so prepositional and principal-word uses should not be collapsed into one rule.
