Title Capitalization Rules: The Complete Guide | TitleCasePro

Title capitalization is the practice of determining which words in a heading should begin with a capital letter. It sounds simple — but the rules differ significantly depending on which style guide you follow, and getting it wrong in an academic paper, a published article, or a professional document signals carelessness.

This is the complete reference. It covers all nine major style guides, explains the rules for each, shows real examples, and addresses the most common mistakes.

The Core Principle Behind Title Case

Every title case style guide starts from the same basic idea:

Principal words get capitalized. Minor words stay lowercase (unless they appear at the start or end of the title).

The disagreement between style guides is entirely about how to define “principal” and “minor.” Specifically:

• Are prepositions like about, between, through principal or minor?
• Does the length of a preposition change its status?
• Are all coordinating conjunctions always minor?

Different style guides answer these questions differently. That’s why the same title looks different in APA vs. Chicago vs. AP.

Universal Rules (All Styles)

These three rules apply in every title case style guide, with no exceptions:

1. The first word is always capitalized — even if it’s a, an, the, or a preposition.
2. The last word is always capitalized — even if it’s a, an, in, or of.
3. Proper nouns are always capitalized — names of people, places, organizations, languages, brands.

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The Nine Style Guides

APA — American Psychological Association, 7th Edition

Used in: Psychology, social sciences, education, nursing, business research.

Rule: Lowercase all prepositions regardless of length. Capitalize nouns, verbs, adjectives, adverbs, pronouns.

Example: A Comprehensive Guide to Writing about the Effects of Climate Change

Full APA rules →

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Chicago — Chicago Manual of Style, 17th Edition

Used in: Book publishing, history, humanities, general non-fiction.

Rule: Lowercase prepositions of 4 letters or fewer. Capitalize prepositions of 5+ letters.

Example: A Comprehensive Guide to Writing About the Effects of Climate Change (Note: “About” = 5 letters → capitalized)

Full Chicago rules →

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AP — Associated Press Stylebook

Used in: US newspapers, broadcast journalism, press releases.

Rule: Capitalize any word of 4 or more letters, regardless of its grammatical category.

Example: A Comprehensive Guide to Writing About the Effects of Climate Change

Full AP rules →

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MLA — Modern Language Association, 9th Edition

Used in: Literary criticism, language study, English courses.

Rule: Lowercase all prepositions regardless of length (same as APA). Capitalize principal words.

Example: A Comprehensive Guide to Writing about the Effects of Climate Change

Full MLA rules →

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Bluebook

Used in: Legal writing, law review articles, court documents.

Rule: Similar to Chicago — lowercase short prepositions, capitalize longer ones.

Example: A Comprehensive Guide to Writing About the Effects of Climate Change

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AMA — American Medical Association, 11th Edition

Used in: Medicine, health sciences, nursing journals.

⚠️ AMA capitalizes every word — articles, prepositions, and conjunctions included. It is the most distinctive of all nine styles.

Example: A Comprehensive Guide To Writing About The Effects Of Climate Change

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NY Times

Used in: New York Times editorial content.

Rule: Capitalize words of 4+ letters (similar to AP), with specific house style exceptions.

Example: A Comprehensive Guide to Writing About the Effects of Climate Change

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Wikipedia

Used in: Wikipedia article titles and section headings.

Rule: Sentence case — only the first word and proper nouns are capitalized.

Example: A comprehensive guide to writing about the effects of climate change

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Email

Used in: Professional email subject lines.

Rule: Sentence case — same as Wikipedia style.

Example: A comprehensive guide to writing about the effects of climate change

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Comparison: Same Title Across All Nine Styles

Title: “A Guide to Writing About the World Without Fear”

Style	Result
APA	A Guide to Writing about the World without Fear
Chicago	A Guide to Writing About the World Without Fear
AP	A Guide to Writing About the World Without Fear
MLA	A Guide to Writing about the World without Fear
Bluebook	A Guide to Writing About the World Without Fear
AMA	A Guide To Writing About The World Without Fear
NY Times	A Guide to Writing About the World Without Fear
Wikipedia	A guide to writing about the world without fear
Email	A guide to writing about the world without fear

Key differences to notice:

• about and without are lowercase in APA/MLA, capitalized in Chicago/AP/Bluebook/AMA/NYT
• AMA capitalizes everything — even To, The, Of
• Wikipedia and Email are sentence case (only “A” is capitalized)

Use the compare tool to see any of your own titles across all nine styles simultaneously.

Key Differences by Word Category

Word category	APA	Chicago	AP	MLA	AMA
Nouns	✅	✅	✅	✅	✅
Verbs (is, are, be)	✅	✅	✅	✅	✅
Adjectives	✅	✅	✅	✅	✅
Articles (a, an, the)	❌	❌	❌	❌	✅
Short prepositions (≤ 4 letters)	❌	❌	❌	❌	✅
Long prepositions (5+ letters)	❌ (lowercase)	✅	✅	❌ (lowercase)	✅
Coord. conjunctions (and, but)	❌	❌	❌	❌	✅

The Most Common Title Capitalization Mistakes

1. Lowercasing verbs

“How to write better” should be “How to Write Better” — Verbs like write, run, be, is, are are always capitalized.

2. Lowercasing “is”

Many people treat is as a minor word because it’s short. It is a verb (linking verb) and is always capitalized in all title case styles.

3. Not capitalizing after a colon

The first word following a colon or em dash is always capitalized.

• ❌ Writing Titles: a practical guide
• ✅ Writing Titles: A Practical Guide

4. Lowercasing the last word

The last word is always capitalized.

• ❌ A Guide to Writing for the
• ✅ A Guide to Writing for The

5. Capitalizing “and,” “but,” “or”

Coordinating conjunctions stay lowercase in all title case styles (except AMA).

Which Style Should You Use?

Field / context	Recommended style
Psychology, social sciences	APA
Book publishing, humanities	Chicago
Journalism, press releases	AP
Literary criticism, English	MLA
Legal writing, law review	Bluebook
Medicine, health sciences	AMA
New York Times editorial	NY Times
Wikipedia, encyclopedias	Wikipedia
Professional email subjects	Email

When no style is specified: Chicago is the safest default for formal writing. AP is the safest default for journalism and marketing copy. When in doubt, check with your instructor, editor, or the publication’s style guide.

Use the title capitalizer to apply any of these nine styles to your title in seconds, with a word-by-word explanation of every capitalization decision.