What words should always be capitalized in a title?

Across all major style guides, the first and last words of a title or headline are always capitalized. Additionally, all major words—including nouns, pronouns, verbs (and linking verbs), adjectives, and adverbs—must be capitalized regardless of where they appear.

Which words are kept lowercase in title case capitalization?

Minor words are lowercased unless they are the first or last word of a title or subtitle. Minor words include articles (a, an, the), short prepositions (such as in, of, on, at, by, to), and short conjunctions (such as and, but, or, for, nor).

How does APA 7th edition handle four-letter prepositions in titles?

Under APA 7th edition rules, any word containing four letters or more is defined as a major word and must be capitalized in title case. This includes four-letter prepositions such as With, From, and Between.

Is the infinitive word "to" capitalized in headlines?

Treatment of "to" in infinitives depends on the style guide: the Associated Press (AP) Stylebook requires capitalizing "to" in infinitives (e.g., "I Want To Play Guitar"), whereas Chicago, Bluebook, and AMA guidelines keep "to" lowercased.

Why are article titles written in sentence case in APA Style reference lists?

APA Style uses sentence case for article and book titles in reference list entries to maintain citation clarity. This formatting tradition dates back to the original 1929 publication standards of APA Style.

Title Capitalization Rules: Complete Style Guide Reference & Examples

Title capitalization rules require capitalizing the first and last words of a title or heading, alongside all major words, which include nouns, verbs (including linking verbs), adjectives, adverbs, and pronouns. Minor words—specifically articles, short prepositions, and short conjunctions—remain lowercased unless they occupy the first or last position, start a subtitle, or follow structural punctuation such as a colon or em dash. Exact formatting varies according to the governing style guide, as systems like APA, Chicago, AP, MLA, AMA, and Bluebook enforce distinct rules regarding word-length thresholds, preposition treatment, and hyphenated compounds.

Fundamental Title Capitalization Rules Across Major Style Guides

Title case, also referred to as headline case, is the standard capitalization style used for titles of books, articles, reports, periodicals, movies, plays, and headings within written works. While specific conventions differ between professional organizations, all major style guides share core foundational principles regarding which words must be capitalized.

Universal rules accepted across nearly all major style manuals include:

First and Last Words: Always capitalize the first and last word of a title or heading, regardless of the word’s part of speech or length.
Subtitles and Major Punctuation: Always capitalize the first word of a subtitle, as well as the first word immediately following a colon, em dash, or end punctuation in a heading.
Major Words: Capitalize all major grammatical parts of speech, which encompass nouns, pronouns, verbs (including linking verbs and phrasal verbs such as “play with”), adjectives, and adverbs.

Differences arise primarily in how style guides classify and treat minor words, which generally include articles (a, an, the), short prepositions, and short conjunctions. Style guides set specific definitions and length thresholds for these categories:

APA Style (7th Edition): Defines major words as nouns, verbs, adjectives, adverbs, pronouns, and any word containing four letters or more (such as With, Between, or From). Lowercases only minor words that are three letters or fewer, which consist of short conjunctions (and, as, but, for, if, nor, or, so, yet), articles (a, an, the), and short prepositions (as, at, by, for, in, of, off, on, per, to, up, via).
Associated Press (AP) Stylebook (2020, 55th Edition): Requires capitalizing all principal words as well as any preposition or conjunction containing four letters or more. Articles (a, an, the) are lowercased. Notably, AP style explicitly mandates capitalizing the word to in infinitives (for example, I Want To Play Guitar).
The Chicago Manual of Style: Capitalizes major words and lowercases conjunctions (and, but, for, or, nor), articles (a, an, the), and the words to and as. Historically, in its 15th edition, Chicago lowercased all prepositions regardless of length unless they were stressed, used adverbially/adjectivally, or functioned as conjunctions. However, updated guidance in the 18th edition (2024) mandates capitalizing prepositions of more than four letters.
AMA Manual of Style (11th Edition): Capitalizes major words (nouns, pronouns, adjectives, verbs, adverbs, and subordinate conjunctions). Lowercases articles (a, an, the), coordinating conjunctions, prepositions of three letters or fewer, and the word to in infinitives.
The Bluebook (21st Edition): Used for legal publications, Bluebook capitalizes nouns, pronouns, adjectives, verbs, adverbs, and subordinate conjunctions. It lowercases articles (a, an, the), coordinating conjunctions, prepositions of four letters or fewer, and the word to in infinitives.
MLA Handbook (9th Edition): Capitalizes all major words (nouns, verbs including phrasal verbs, adjectives, adverbs, and pronouns) as well as the first word of any title or subtitle.

Comprehensive Style Guide Comparison for Title Capitalization

To apply these rules accurately, compare how each major publishing standard categorizes specific grammatical elements and word lengths:

Style Guide	First & Last Word	Words ≥ 4 Letters Capitalized?	Preposition Capitalization Rule	Conjunction Capitalization Rule	Infinitive “To” Rule	Subtitle First Word Capitalized?
APA 7th Ed.	Always Capitalized	Yes (All words of 4+ letters capitalized)	Lowercase prepositions of 3 letters or fewer; capitalize 4+ letters	Lowercase short conjunctions (3 letters or fewer)	Lowercase (2 letters)	Always Capitalized
AP Stylebook (2020)	Always Capitalized	Yes (Prepositions & conjunctions 4+ letters)	Lowercase prepositions of 3 letters or fewer; capitalize 4+ letters	Lowercase conjunctions of 3 letters or fewer; capitalize 4+ letters	Capitalized (To)	Always Capitalized
Chicago (18th Ed.)	Always Capitalized	Prepositions > 4 letters only	Lowercase prepositions of 4 letters or fewer; capitalize > 4 letters	Lowercase and, but, for, or, nor	Lowercase (to)	Always Capitalized
Chicago (15th Ed.)	Always Capitalized	No	Lowercase prepositions regardless of length (unless stressed/adverbial)	Lowercase and, but, for, or, nor	Lowercase (to)	Always Capitalized
AMA 11th Ed.	Always Capitalized	No	Lowercase prepositions of 3 letters or fewer	Lowercase coordinating conjunctions; capitalize subordinate	Lowercase (to)	Always Capitalized
Bluebook 21st Ed.	Always Capitalized	No	Lowercase prepositions of 4 letters or fewer	Lowercase coordinating conjunctions; capitalize subordinate	Lowercase (to)	Always Capitalized
MLA 9th Ed.	Always Capitalized	Applies to major words	Lowercase short prepositions	Lowercase short conjunctions	Lowercase (to)	Always Capitalized

Worked Capitalization Example Applied Step-by-Step

To see how these theoretical rules work in practice, examine the step-by-step conversion of an uncapitalized raw title under three distinct style manuals.

Raw Input Title: learning to live with artificial intelligence: a guide for working on and off the grid

Word-by-Word Analysis

learning: First word of the title. Capitalized in all styles → Learning
to: Infinitive marker (2 letters). APA 7th, Chicago, Bluebook, and AMA lowercase minor words ≤ 3 letters → to. AP Stylebook specifically requires capitalizing to in infinitives → To.
live: Verb. Major word capitalized in all styles → Live
with: Preposition (4 letters). APA 7th capitalizes all 4-letter words → With. AP Stylebook capitalizes 4-letter prepositions → With. Chicago 18th edition lowercases prepositions of 4 letters or fewer → with (Chicago 15th also lowercases prepositions regardless of length → with).
artificial: Adjective. Major word capitalized in all styles → Artificial
intelligence: Noun. Major word capitalized in all styles → Intelligence
:: Colon separating main title from subtitle.
a: Article following colon (first word of subtitle). Capitalized across APA, Chicago, AP, MLA, and AMA → A
guide: Noun. Major word capitalized in all styles → Guide
for: Preposition/conjunction (3 letters). Lowercase across APA, AP, Chicago, Bluebook, and AMA → for
working: Verb (gerund). Major word capitalized in all styles → Working
on: Preposition (2 letters). Lowercase across all styles → on
and: Coordinating conjunction (3 letters). Lowercase across all styles → and
off: Preposition (3 letters). Lowercase across APA 7th (≤ 3 letters), AP, Chicago, and Bluebook → off
the: Article (3 letters). Lowercase across all styles → the
grid: Noun and final word of title. Capitalized in all styles → Grid

Final Converted Titles by Style Guide

APA Style (7th Edition): “Learning to Live With Artificial Intelligence: A Guide for Working on and off the Grid”
AP Stylebook (2020 Edition): “Learning To Live With Artificial Intelligence: A Guide for Working on and off the Grid”
Chicago Manual of Style (18th Edition): “Learning to Live with Artificial Intelligence: A Guide for Working on and off the Grid”

When managing large bodies of text or converting headlines between different house styles, relying on an automated Case Converter simplifies the workflow while adhering precisely to target style manual standards.

Variations by Context, Hyphenation, and Edition Updates

Beyond basic part-of-speech rules, title capitalization involves complex edge cases such as hyphenated compounds, scientific nomenclature, and contextual publication rules.

Hyphenated Compounds and Prefixes

Style guides handle hyphenated words within titles according to specific structural rules:

APA 7th Edition: Capitalizes both parts of a hyphenated major word (e.g., Self-Report). However, if a hyphenated prefix (such as Mid-, Anti-, or Super-) is attached to a compound modifier, the second word remains lowercased (e.g., Mid-year, Anti-hero).
Chicago Manual of Style Evolution: In the 15th edition, Chicago lowercased the second word after a hyphenated prefix in compound modifiers (Mid-year, Anti-hero). Starting with the 17th edition (2010), Chicago updated this rule to capitalize the second word after a hyphenated prefix (Mid-Year, Anti-Hero).
AMA 11th Edition: Lowercases the second word in a hyphenated compound when it functions as a prefix or suffix (e.g., Anti-itch, World-wide) or part of a single word. If both parts are equal words rather than prefixes or suffixes, the second word is capitalized (e.g., Cost-Benefit).

Scientific Terms and Nomenclature

Specialized disciplines follow unique capitalization guidelines for titles:

AMA 11th Edition: In botanical and zoological species names, capitalize the genus name but lowercase the species epithet (e.g., Homo sapiens). For chemical compounds featuring Greek letters, capitalize the first non-Greek letter following a lowercase Greek letter (e.g., ω-Bromohexanoic), but lowercase the first non-Greek letter following a capital Greek letter (e.g., Δ-9-tetrahydrocannabinol).
Chicago Manual of Style: Requires lowercasing the second part (the specific epithet) of scientific names of organisms.

Contextual Application: Title Case vs. Sentence Case

Style manuals restrict where title case is applied versus sentence case (where only the first word and proper nouns are capitalized):

APA Style 7th Edition Usage: Title case is required for titles of articles, books, reports, and other works when mentioned inside body text (e.g., Train Your Mind for Peak Performance: A Science-Based Approach for Achieving Your Goals). It is also mandatory for test and measure names (e.g., Beck Depression Inventory–II), all paper headings from Levels 1 through 5, named paper sections (e.g., the Results section), periodical titles (e.g., Journal of Latinx Psychology, Chicago Tribune), table titles, figure titles, axis labels, and legends.
APA Reference Lists: Article and book titles in APA reference list citations use sentence case rather than title case—a convention dating back to the founding guidelines of APA Style in 1929.