A phonestheme (/foʊˈnɛsθiːm/; phonaestheme in British English), coined in 1930 by British linguist J. R. Firth (from the Greek φωνή phone, "sound", and αἴσθημα aisthema, "perception" from αίσθάνομαι aisthanomai, "I perceive"), is a basic unit of sound or sounds systematically paired with a certain meaning in a language. Such pairing would violate the arbitrariness principle of semantics. A phonestheme is different from a phoneme (a basic unit of word-differentiating sound) or a morpheme (a basic unit of meaning) because it does not meet the normal criterion of compositionality.