letters

Letters have two common meanings. In writing systems, a letter is a basic symbol that, together with others, forms an alphabet and stands for one or more sounds. In correspondence, a letter is a written message sent from one person to another (or to an organization). Some discussions use both senses within the same article.

Letters are the building blocks of alphabets. Each letter is a grapheme, a written representation of a phoneme or group of phonemes. In alphabetic scripts, letters are organized in a set with a conventional order and often appear in two case forms: uppercase (capital) and lowercase. The shape of letters can vary across languages and fonts, and many alphabets include letters with diacritics or ligatures to indicate pronunciation, tone, or distinction between words.

Historically, alphabetic writing emerged in the Near East around the second millennium BCE, with the Phoenician alphabet influencing Greek and, through it, Latin and other scripts. Latin letters form the basis of the most widely used alphabet today. In medieval manuscripts, lowercase forms developed as scribes wrote in cursive; printing from moveable type later standardized letter shapes and spacing across many languages.

Letters as mail have formal conventions. A personal or official letter typically begins with a salutation, proceeds to a body of text, and ends with a closing and signature. Addresses and postage rules govern delivery, while electronic letters (email) follow digital formats. Letter writing is a cultural practice with varying norms for tone and formality.

Beyond these senses, some languages use scripts where the concept of a single letter may differ. In non-alphabetic systems such as logographic writing, characters often represent morphemes or words rather than sounds. Still, in alphabet-based systems, the study and use of letters remains central to literacy and communication.