Phonology

The fundamental unit of linguistics is the sign, which, as a first approximation, can be defined as a conventional pairing of sound and meaning. By conventional we mean both that signs are handed down from generation to generation with little modification and that the pairings are almost entirely arbitrary, just as in bridge, where there is no particular reason for a bid of two clubs in response to one no trump to be construed as an inquiry about the partner's major suits. One of the earliest debates in linguistics, dramatized in Plato's Cratylus, concerns the arbitrariness of signs. One school maintained that for every idea there is a true sound that expresses it best, something that makes a great deal of sense for onomatopoeic words (describing e.g. the calls of various animals) but is hard to generalize outside this limited domain. Ultimately the other school prevailed (see Lyons 1968 Sec. 1.2 for a discussion) at least as far as the word-level pairing of sound and meaning is concerned.