Capitalisation

Capitalisation, in British English often spelled capitalisation and in American English capitalization, is the practice of writing a word with an initial capital letter. Its main purpose is to signal proper nouns, sentence boundaries, and certain emphasis, aiding readability and clarity. Spelling varies by dialect, with British usage favouring capitalisation and American usage capitalization.

Core rules in English include: capitalising the first word of a sentence; capitalising proper nouns such as personal names (Jane), places (London), organisations (United Nations), and titles that form part of a name (Queen Elizabeth II). The pronoun I is always capitalised. Days of the week, months, nationalities, languages, and holidays are capitalised, while many common nouns are not. Seasons are generally not capitalised unless they are personified or part of a specific title.

In titles and headings, capitalization follows conventions such as title case, where most major words are capitalised and short articles, conjunctions, and prepositions are often lowercase unless they begin or end the title. After a colon, capitalization rules vary by style guide; some require capitalising the following word if it forms a complete sentence.

Acronyms and initialisms are typically written in uppercase (NASA, UNESCO). Brand names may employ distinctive capitalization for branding purposes. In other languages, capitalization rules differ; for example, German capitalises all nouns, while French uses mixed rules that depend on context.

Overall, capitalisation supports syntax and meaning, while conventions can vary by language, style guide, and typographic practice.