phoneme

The smallest meaningful unit in the sound system of a language. For example, the word is has two phonemes: /i/ and /s/; ship has three phonemes: /sh/, /i/, /p/. A phoneme usually has several manifestations dependent on varying phonological contexts. For example, the p in pin and spin differs slightly in pronunciation but is regarded as being the same phoneme; that is, as having the same functional meaning within each word.