kirjain

Kirjain is a Finnish term for a single letter of an alphabet, i.e., a grapheme used to represent a sound in writing. It is the basic unit of written language, combining with other letters to form words and sentences. In most scripts, a kirjain exists in uppercase and lowercase forms.

An etymology note: the word kirja means "book"; kirjain literally signals a character used in writing words. While commonly used to refer to letters of the Latin alphabet in Finnish, the term can describe any character that functions as a letter in a writing system.

Finnish uses the basic Latin alphabet plus the diacritics ä and ö to represent specific sounds; these two letters are considered separate kirjain from a and o. Other languages add diacritics or ligatures to letters; a kirjain may be simple or accented.

In digital writing, each kirjain is encoded as a code point in Unicode, allowing consistent representation across platforms. Early computing relied on ASCII, which covered only the unaccented Latin letters, prompting the expansion to extended encodings and fonts to render diacritics properly.

Historically, the Latin alphabet arrived in Finland with Christianization and printing; orthography has been standardized during the 19th and 20th centuries. Today, kirjain remains a core concept in linguistics and typography, describing the basic symbols used to write Finnish and other languages.