Capitalizing

Capitalizing is the practice of converting letters to their uppercase form, commonly used to mark the beginning of a sentence, proper nouns, acronyms, and certain other elements of written language. It helps signal structure, emphasize names, and aid readability. While the basic idea is shared across languages, specific rules vary by language and style guide.

In English, capitalization typically applies to the first letter of sentences and to proper nouns (such as people, places, and organizations). The pronoun I is always capitalized. Days of the week, months, holidays, and official names of institutions are capitalized, as are acronyms and initialisms (NASA, UNESCO). Titles and headings follow style rules that often distinguish between major and minor words, with variations across style guides.

Heading and title conventions often distinguish between title case and sentence case. Title case generally capitalizes major words, while an accompanying style guide may require small words (articles, conjunctions, prepositions) to be lowercase unless they are first or last in the title. Sentence case capitalizes only the first word of the sentence and proper nouns.

Capitalization rules differ by language. German capitalizes all nouns, a distinctive feature of that language. Turkish has rules that involve dotted and dotless I, influencing capitalization. Other languages and scripts may have different conventions or minimal capitalization. Some languages do not rely on capitalization to convey word boundaries in the same way as Latin-script languages.

In digital and typesetting contexts, capitalization also interacts with typography and coding conventions. In programming, case sensitivity means capitalization distinguishes identifiers (variable names, function names), and common conventions include camelCase, PascalCase, or all-lowercase identifiers. All-caps is sometimes used for emphasis but is generally avoided in continuous text.