In sociolinguistics, a register is a variety of language used for a particular purpose or particular communicative situation. Wikipedia

A form of a language used for a particular purpose or in a particular social setting Wikipedia Disambiguation

Form of language used for a particular purpose or in a particular communicative situation Wikidata

Levels of a language that differ in vocabulary, grammar and style. The choice of the level depends on outside factors, such as the relationship between the speakers, the medium of communication (talk, letter, phone, e-mail) and the situation the communication takes place in. OmegaWiki

A style of a language used in a particular context. Wiktionary

Linguistics: style of a language used in a particular context. Wiktionary (translation)