The basis for phonological analysis is the notion of distinctiveness. In the structuralist period, attention was focussed on distinctions between phonemes. Since the beginning of the generative period, the primary unit has rather been the distinctive feature. The fundamental notion remains the same. It is constituted by the idea that a phonetic difference is to be regarded as a phonological difference if and only if it is linked with a difference in meaning. Thus, in the final analysis, the evidence for distinctiveness is to be found in linguistic communication. If a certain phonetic distinction is regularly used to convey distinctions in meaning, it is phonologically distinctive.