phoneme

n. A phoneme is an abstract mental representation of a sound or family of sounds. The collection of phonemes for a language is referred to as that language's phonemic inventory. Within a phonemic inventory, different phonemes are contrastive with respect to each other: replacing one with another in a word results in a change in meaning. Contrastive differences can be diagnosed by finding minimal pairs, pairs of words that differ only in terms of the two sounds in question: /t/ and /d/ are contrastively different in English (minimal pair: bet, bed), /t/ and the flap /R/ are contrastively different in Spanish (minimal pair: pata “duck,” para “for”). Families of sounds that are not contrastively different in a language are called allophonic variants, or allophones, of the same underlying phoneme. Two allophones are in complementary distribution when the contexts in which one occurs differ from the contexts in which the other occurs. In English, the two allophones of /t/, aspirated [t?] and the flap [R], are in complementary distribution: flaps only occur intervocalically (between two vowels) as the onset consonants of unstressed syllables. Allophones of a single phoneme are usually perceived by native speakers of a language as belonging to the same category. For example, words such as top, stop, baton, butter, beat illustrate the range of English allophones for the phoneme /t/. – EMF