A phoneme is a basic unit of a language's phonology, which is combined with other phonemes to form meaningful units, morphemes. The phoneme can be described as "The smallest contrastive linguistic unit which may bring about a change of meaning".In this way the difference in meaning between the English words kill and kiss is a result of the exchange of the phoneme /l/ for the phoneme /s/. Two words that differ in meaning through a contrast of a single phoneme form a minimal pair.