“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.
ReviewedEvidence2 sourcesSectionWriting & Style
Quick answer
APA 7 normally capitalizes “Than” because words of four letters or more are major words. Chicago 18 is context-sensitive: lowercase “than” when it functions as a preposition, but capitalize “Than” when it functions as a conjunction. That means a reliable Chicago converter must parse the construction rather than rely on a fixed word list.
Key details
APA 7capitalize as a four-letter major word
Automation Classrequires POS/syntactic override in Chicago 18
Chicago 18lowercase as preposition; capitalize as conjunction
Wordthan
Word Classpreposition or conjunction
Style-by-style guidance
APA 7
APA’s four-or-more-letter major-word rule makes “than” capitalized in ordinary title case, regardless of the Chicago distinction described below.
Further guidance
Chicago Conjunction
Chicago capitalizes “Than” when it introduces a clause, including clauses with an understood or omitted verb.
Chicago Preposition
Chicago gives the example “There Is More than One Path to a Successful Meal,” analyzing “than” as a preposition because the following noun acts as its object.
Converter Consequence
This is a high-value regression case: the token “than” cannot receive one fixed Chicago capitalization value without looking at syntax.
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.
“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.
“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.
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.
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.
APA capitalizes “After” 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.
Related across sections
These links are manually reviewed for a genuine cross-section connection.
“Then” usually concerns time, sequence, addition, or result; “than” introduces comparison. Because the words are similar in sound and spelling, a meaning-based substitution test is more reliable than memorizing a single example.
