MLA 9 describes title style as capitalizing the first word, last word, and all principal words. MLA’s public Style Center also documents the traditional lowercase treatment of internal prepositions, but its detailed preposition article is edition-labeled for MLA 8, so this engine does not yet treat the full MLA 9 converter profile as complete.
ReviewedEvidence3 sourcesSectionWriting & Style
Quick answer
For MLA 9, capitalize the first word, last word, and principal words. Internal prepositions are normally lowercase in MLA editorial guidance, but the full automated MLA 9 rule profile is not treated as fully deterministic here until all current-edition edge cases are independently covered.
Core RuleCapitalize first word, last word, and principal words
EditionMLA Handbook, 9th edition (2021)
Internal PrepositionsNormally lowercase in MLA editorial guidance
Profile Idmla-9
Important caveats
Automation boundary
This record is public because the human-facing rule is useful and adequately sourced. Automatic MLA conversion is not treated as fully deterministic until compounds, phrasal structures, subtitles, punctuation boundaries, and other current-edition exceptions have deterministic tests.
Further guidance
Current Ninth Edition Core
The MLA Style Center’s ninth-edition handout guidance says to capitalize the first word, the last word, and all principal words when a title is styled in title case.
English And Other Languages
MLA’s Style Center explains that English-language titles use headline/title style, while titles in other languages can follow language-specific sentence-style conventions.
Prepositions
MLA’s official Style Center guidance has long treated internal prepositions as lowercase regardless of length. The detailed public article carrying that rule is explicitly labeled for the eighth edition, so the rule is retained as editorial evidence but not used alone to certify a complete ninth-edition automation profile.
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.
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.
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.
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.
The word “and” is normally lowercase in the middle of a title because it is a coordinating conjunction, but first-word, last-word, and style-specific rules can change the answer.
“Of” is normally lowercase in the middle of a title in APA 7, Chicago 18, and MLA-style title capitalization because it is a short preposition. First- or last-word position can override the ordinary middle-of-title treatment.
“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.
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.
