Each binary contrast between groups of phonemes can be expressed by the (contrast between the) occurrence and non-occurrence of a particular component in the unique combination of components which will indicate each of these phonemes. Suppose we are able to state not that there are, say, four stop positions /p, t, k, q/ in a language, but that there is one binary contrast between /p, t/ and /k, q/, and another between /p, k/ and /t, q/. Then each contrast can be expressed by a component, such that one contrasting group has the component while the other lacks it.
- Harris (1951), a pag.147, n.51