The term phoneme is applied to the minimal unit of speech capable of changing meaning in a given language or language variety. The nature of the phoneme was subject to discussion within linguistics, with some proposing a physical reality, and others a psychological status. Current views tend to support an abstract linguistic status, though many current phonological theories no longer give a central role to the phoneme.

The semantic contrastive nature of the phoneme can be seen, for example, in the use of the English [Page 1357]sounds [p] and [k] in the words pat and cat. These words contrast only through the change in the initial consonants, thus these consonants belong to separate phonemes, shown through the use of slant brackets: /p/, /k/. A minimal pairs ...