Kirjainmerkki

Kirjainmerkki is a Finnish term that refers to a letter character—an element used to represent a phoneme or sound within a writing system. In practice, it denotes any symbol that functions as a letter of an alphabet, including basic Latin letters as well as letters with diacritics common in various languages. It excludes digits, punctuation, and symbols that do not serve as letters.

In typography, a kirjainmerkki has properties such as case (uppercase and lowercase), as well as potential diacritics and ligatures. Letters can exist in single-codepoint form or as part of extended character sets, and their shapes can vary between fonts. The concept is central to orthography, lexicon, and typesetting across languages.

In digital text, letters are encoded as code points in standards like Unicode. Each letter—such as the Latin small letter a or the Latin capital letter Ä—has a specific code point. Some letters with diacritics can be represented directly as single code points or formed by combining base letters with combining diacritical marks. Normalization forms (for example NFC and NFD) describe how these representations are stored and compared.

Orthography varies by language. The official Finnish alphabet contains 29 letters, including ä, ö, and å, reflecting its use of diacritics and loanwords. Kirjainmerkit form the basis of spelling, proper nouns, and phonological representation in Finnish and other languages, and they are a fundamental unit in linguistic analysis, typography, and digital text processing. See also character, letter, and Unicode.