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Guide & Reference
Whether you're writing a research paper, a news headline, a Wikipedia article, or a marketing email — capitalization rules differ widely across style guides. This guide breaks down every style, answers the most common questions, and helps you pick the right one for your work.
Title case is a capitalization style where most words in a title or heading begin with a capital letter. The key nuance is that minor words — short prepositions, articles, and conjunctions — are generally left lowercase unless they open or close the title.
Title case is the default for book titles, film titles, song names, academic paper headings, news headlines, and most professional documents. It signals that a phrase is a proper title rather than plain prose.
Sentence case capitalizes only the first word of a title and any proper nouns — exactly like a normal sentence. It reads as more conversational and is increasingly common in digital and product contexts.
Use sentence case for UI labels, app navigation, blog subtitles, and anywhere a formal headline feels out of place. Many tech companies (Notion, Linear, Figma) use sentence case throughout their interfaces for a cleaner look.
APA (American Psychological Association) style is used primarily in psychology, education, and social sciences. In APA title case, all major words are capitalized — nouns, verbs, adjectives, adverbs — while articles (a, an, the), short prepositions (of, in, on, at, by, for, to, up, via), and coordinating conjunctions (and, but, or, nor) are lowercased unless they're the first or last word.
Title length: APA recommends titles be no longer than 12 words for journal articles. Dissertation and thesis titles can be longer but should remain specific and concise. Running heads are truncated to 50 characters.
The Chicago Manual of Style (CMOS) is the standard for books, history, literature, and arts publishing. Chicago title case is similar to APA but slightly stricter — it lowercases the same minor words but explicitly requires capitalizing all verbs (including short ones like "Is", "Are", "Be") and all adjectives regardless of length.
Title length: Chicago has no hard word limit, but recommends keeping titles under 10 words for readability. Subtitles after a colon begin with a capital letter.
AP (Associated Press) style is the standard for journalism, newspapers, and online news. AP title case capitalizes all words of four letters or more and lowercases short conjunctions, articles, and prepositions of three letters or fewer.
Title length: AP headlines are typically 5–10 words and prioritize scannability. AP style generally avoids subtitles in headlines.
MLA (Modern Language Association) style is used in humanities — literature, language, and cultural studies. MLA title case is similar to Chicago: capitalize all major words, lowercase articles, short prepositions, and coordinating conjunctions.
Title length: No strict limit, but MLA recommends titles that are specific and descriptive. Works Cited entries truncate long titles using an ellipsis.
BB (Bluebook) is used for legal writing — court documents, law reviews, and citations. Bluebook title case follows Chicago-like rules: capitalize all major words, lowercase minor function words.
AMA (American Medical Association) style is used in medical and health science publishing. AMA title case capitalizes all words of four or more letters, similar to AP, and lowercases short articles and prepositions. AMA recommends titles under 150 characters for journal submissions, and structured abstracts must follow strict word limits (usually 250 words).
NYT (New York Times) follows a house style close to AP but with some proprietary rules. The Times capitalizes most words in headlines and uses a slightly more aggressive capitalization than AP for prepositions. Headline length targets 6–9 words for print; digital headlines are often longer for SEO.
Wikipedia uses sentence case for almost everything — article titles, section headings, and captions. Only proper nouns, acronyms, and the first word of a title are capitalized. This is a deliberate choice to avoid over-formalization and to make automated linking easier. The only exception is official proper names (laws, organizations, works) which follow their real-world capitalization.
Email subject lines have no universal standard — but the choice of capitalization affects open rates and tone. There are three common approaches:
Length: Keep subject lines to 40–60 characters (6–10 words) to avoid truncation on mobile. Preview text adds another 35–90 characters of context. Avoid ALL CAPS — it triggers spam filters and reads as shouting.
Yes — always. Verbs are always capitalized in title case, regardless of their length. This includes short verbs like "Is", "Are", "Was", "Be", "Do", "Go", "Has", and "Had". A common mistake is treating short words as minor words — but only articles, coordinating conjunctions, and short prepositions get lowercased, never verbs.
It depends on the style guide and the length of the preposition:
Across all style guides, certain words are always capitalized:
For digital publishing and web content, curly (smart) quotes are typographically correct: "like this" and 'like this'. Most word processors and CMSs convert straight quotes automatically.
For plain text environments — code, CSV files, emails sent as plain text, or any system where encoding matters — use straight quotes (" and ') to avoid encoding issues. The "Straight quotes" toggle in the converter above handles this automatically.