Allophone

allophone, one of the phonetically distinct variants of a phoneme (q.v.). The occurrence of one allophone rather than another is usually determined by its position in the word (initial, final, medial, etc.) or by its phonetic environment. Speakers of a language often have difficulty in hearing the phonetic differences between allophones of the same phoneme, because these differences do not serve to distinguish one word from another. In English the t sounds in the words “hit,” “tip,” and “little” are allophones; phonemically they are considered to be the same sound although they are different phonetically in terms of aspiration, voicing, and point of articulation. In Japanese and some dialects of Chinese, the sounds f and h are allophones.