Redundancy enters actual systems in two ways: (1) absolute limitations on sequence, such as the fact that in written English Q is invariably followed by U; (2) variations in relative frequency of different sequences, such as the relatively common occurence of ST as over against the rather rare occurence of SCH. The communicative importance of redundancy is that errors of transmission—collectively called ‘noise’ in information theory—are inevitable; a certain amount of redundancy prevents this inevitable measure of noise from destroying communication altogether.
- Hockett (1958), Pag. 88-89

The full import of the stringent limitations on the arrangements in which phonemes occur can only be understood in terms of ‘redundancy’. In everyday parlance, this word means saying more than is strictly necessary. [...].
- Hockett (1958), Pag. 87