Phonemes

The basic unit of study of phonology is the phoneme, which may be defined as sets of phones which function as one unit in a language, and provide contrast between different words. In other words, a phoneme is a category that speakers of a language put certain sounds into. For instance, returning to the Tok Pisin example above, the sounds [s] and [t] would both belong to the phoneme /t/. (In the IPA, phonemes are conventionally enclosed in forward slashes //.)

As another example, try pronouncing the English words keys and schools carefully, paying close attention to the variety of [k] in each. You should find that in the first there is a noticeable puff of air (aspiration), while in the second it is absent. These words may be written more precisely phonetically as [kʰiz] and [skulz]. However, since aspiration never changes the meaning of a word, both of these sounds belong to the phoneme /k/, and so the phonetic representations of these words are /kiz/ and /skulz/.

It should be evident why it is appropriate to refer to the phoneme as a level of abstraction away from the phone. We have removed a layer of information which, while interesting in itself, does not interact in many aspects of a language.