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Reference guide

Capitalization Rules by Style Guide

Compare how AP, APA, MLA, Chicago, and standard title case handle prepositions, conjunctions, articles, and other tricky words — with a side-by-side table and real examples.

Active style focus: Chicago style guidance

Style Guide Overview

Associated Press Stylebook

The AP Stylebook is the primary reference for journalists, newsrooms, and digital media. It favors readability and consistency in headline casing, capitalizing longer prepositions while keeping short function words lowercase.

  • —Capitalize words with 4 or more letters, including prepositions and conjunctions
  • —Lowercase articles (a, an, the) in middle positions
  • —Always capitalize the first and last word of the title
  • —Capitalize both parts of hyphenated compounds in most cases

Source: AP Stylebook (56th Edition (2024))

APA Publication Manual

The APA Publication Manual is the standard for academic and scientific writing. Its title case rules capitalize words of four or more letters, creating a slightly more capitalized look than AP style.

  • —Capitalize words with 4 or more letters, including prepositions and conjunctions
  • —Lowercase short conjunctions (and, but, or, nor, yet, so, for) under 4 letters
  • —Lowercase short prepositions (at, by, in, of, on, to, up) under 4 letters
  • —Always capitalize the first word after a colon, dash, or end punctuation

Source: APA Style (7th Edition (2019))

MLA Handbook

The MLA Handbook serves humanities scholars and literature students. Its title case conventions are the strictest of the major guides: all prepositions stay lowercase in middle positions regardless of length.

  • —Capitalize the first and last word of the title and subtitle
  • —Lowercase articles, prepositions, and coordinating conjunctions in middle positions
  • —Lowercase all prepositions regardless of length, even long ones like "between" or "through"
  • —Capitalize the first word after a colon

Source: MLA Handbook (9th Edition (2021))

The Chicago Manual of Style

The Chicago Manual of Style is the gold standard for book publishing and formal editorial work. The 18th edition (2024) capitalizes prepositions of five or more letters, while shorter prepositions and conjunctions stay lowercase in middle positions.

  • —Lowercase articles (a, an, the) in middle positions
  • —Lowercase coordinating conjunctions (and, but, or, nor, yet, so, for)
  • —Lowercase prepositions of four or fewer letters; capitalize prepositions of five or more letters (18th ed.)
  • —Always capitalize the first and last word of title and subtitle

Source: Chicago Manual of Style (18th Edition (2024))

Standard Title Case

Standard title case is a balanced default used when no specific style guide is required. It follows broadly accepted conventions: capitalizing major words while lowercasing most short function words in middle positions.

  • —Capitalize major words (nouns, verbs, adjectives, adverbs)
  • —Lowercase articles, short prepositions, and short conjunctions in middle positions
  • —Always capitalize the first and last word
  • —Capitalize words after colons and major punctuation

Source: Title Case Converter (General convention)

Style Comparison Table

How each style treats the same input. Differences are where editorial consistency matters most.

ScenarioStandardAPAPAMLACHICAGO
Long preposition: "across" (6 letters)
AP, APA, and Chicago (18th ed.) capitalize "across" – it clears every length threshold. Standard and MLA keep it lowercase.
Running across the Bridge at NightRunning Across the Bridge at NightRunning Across the Bridge at NightRunning across the Bridge at NightRunning Across the Bridge at Night
Long preposition: "between" (7 letters)
AP, APA, and Chicago (18th ed.) capitalize "between" (7 letters). MLA keeps all prepositions lowercase regardless of length.
The Cat Is between the BoxesThe Cat Is Between the BoxesThe Cat Is Between the BoxesThe Cat Is between the BoxesThe Cat Is Between the Boxes
Short preposition: "with" (4 letters)
AP and APA capitalize "with" (4-letter threshold). Standard, MLA, and Chicago (5+ letters) keep it lowercase.
Writing with Confidence and PurposeWriting With Confidence and PurposeWriting With Confidence and PurposeWriting with Confidence and PurposeWriting with Confidence and Purpose
Short preposition: "from" (4 letters)
AP and APA capitalize both "from" (4 letters) and "around" (6 letters). Chicago capitalizes only "around" (5+ letters), so "from" stays lowercase.
Ideas from around the WorldIdeas From Around the WorldIdeas From Around the WorldIdeas from around the WorldIdeas from Around the World
Subtitle after colon
All styles agree: the first word after a colon is always capitalized, even articles like "a".
Title Case Rules: A Practical GuideTitle Case Rules: A Practical GuideTitle Case Rules: A Practical GuideTitle Case Rules: A Practical GuideTitle Case Rules: A Practical Guide
Preposition "about" (5 letters)
"About" hits Chicago's 5-letter threshold exactly, so AP (4+), APA (4+), and Chicago (5+) all capitalize it. Standard and MLA do not.
The Rules about Writing and ThinkingThe Rules About Writing and ThinkingThe Rules About Writing and ThinkingThe Rules about Writing and ThinkingThe Rules About Writing and Thinking
Preposition "after" (5 letters)
"Along" reads as part of the verb here, so every style capitalizes it. "After" (5 letters) splits AP, APA, and Chicago from standard and MLA.
She Walked Along the River after LunchShe Walked Along the River After LunchShe Walked Along the River After LunchShe Walked Along the River after LunchShe Walked Along the River After Lunch

Common Edge Cases

Short connectors and prepositions

Input: walking during the light

Current style (chicago): Walking During the Light

Compare all styles
  • Standard: Walking during the Light
  • AP: Walking During the Light
  • APA: Walking During the Light
  • MLA: Walking during the Light
  • CHICAGO: Walking During the Light

The word 'during' changes across styles and is a common source of editorial inconsistency. Chicago's 18th edition (2024) now capitalizes it too.

Subtitle after colon

Input: title case rules: a practical guide for editors

Current style (chicago): Title Case Rules: A Practical Guide for Editors

Compare all styles
  • Standard: Title Case Rules: A Practical Guide for Editors
  • AP: Title Case Rules: A Practical Guide for Editors
  • APA: Title Case Rules: A Practical Guide for Editors
  • MLA: Title Case Rules: A Practical Guide for Editors
  • CHICAGO: Title Case Rules: A Practical Guide for Editors

Subtitles should start clearly after punctuation so the user has a reliable next edit decision.

Hyphenated and branded wording

Input: state-of-the-art workflows for iPhone launches

Current style (chicago): State-of-the-Art Workflows for iPhone Launches

Compare all styles
  • Standard: State-of-the-Art Workflows for iPhone Launches
  • AP: State-of-the-Art Workflows for iPhone Launches
  • APA: State-of-the-Art Workflows for iPhone Launches
  • MLA: State-of-the-Art Workflows for iPhone Launches
  • CHICAGO: State-of-the-Art Workflows for iPhone Launches

Hyphenation and brand casing are frequent edge cases where users should verify output quickly before publishing.

Infinitive "to" vs preposition "to"

Input: to be or not to be

Current style (chicago): To Be or Not to Be

Compare all styles
  • Standard: To Be or Not to Be
  • AP: To Be or Not to Be
  • APA: To Be or Not to Be
  • MLA: To Be or Not to Be
  • CHICAGO: To Be or Not to Be

"To" as the first word is always capitalized. In middle positions, all styles lowercase it whether used as an infinitive marker or preposition.

Short verb "is" in the middle

Input: she is an editor-in-chief

Current style (chicago): She Is an Editor-in-Chief

Compare all styles
  • Standard: She Is an Editor-in-Chief
  • AP: She Is an Editor-in-Chief
  • APA: She Is an Editor-in-Chief
  • MLA: She Is an Editor-in-Chief
  • CHICAGO: She Is an Editor-in-Chief

"Is" is a verb, not a preposition or conjunction, so all styles capitalize it. Many writers mistakenly lowercase short verbs.

4-letter preposition "with"

Input: writing with confidence and purpose

Current style (chicago): Writing with Confidence and Purpose

Compare all styles
  • Standard: Writing with Confidence and Purpose
  • AP: Writing With Confidence and Purpose
  • APA: Writing With Confidence and Purpose
  • MLA: Writing with Confidence and Purpose
  • CHICAGO: Writing with Confidence and Purpose

The 4-letter threshold in AP and APA capitalizes "with," while Chicago (5+ letters) and MLA (all prepositions lowercase) keep it lowercase. It is the most common boundary word.

Frequently Asked Questions

Which capitalization style should I use?

Use the style required by your publication or institution. AP style is standard for journalism and news, APA for academic and scientific papers, MLA for humanities essays, and Chicago for book publishing and formal editorial work.

What is the main difference between AP and Chicago title case?

The key difference is how they treat longer prepositions. AP capitalizes prepositions with 5 or more letters (like "Between" and "Through"), while Chicago keeps all prepositions lowercase in middle positions regardless of length.

Should I capitalize "is" in a title?

Yes. "Is" is a verb (a form of "to be"), and all major styles agree that verbs should always be capitalized in titles, even short ones.

Are there words that are always lowercase in titles?

No word is always lowercase. Even articles like "a", "an", and "the" are capitalized when they appear as the first or last word of a title. In middle positions, articles, short prepositions, and short conjunctions are typically lowercase across all styles.

How do I capitalize a hyphenated word in a title?

Most styles capitalize the first element of a hyphenated compound. For subsequent elements, capitalize them if they are major words (nouns, verbs, adjectives). Keep small function words lowercase, such as "State-of-the-Art" where "of" and "the" stay lowercase.

Popular Capitalization Questions

Specific words and situations the general rules do not fully cover – each answered against AP, APA, MLA, and Chicago.

Next Steps

Try the converter with your own text, or explore style-specific guides in the blog.

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