redundancy (n.)

A term derived from INFORMATION theory and applied to the analysis of the range of features used in making LINGUISTIC contrasts. A FEATURE (of sound, GRAMMAR, etc.) is redundant if its presence is unnecessary in order to identify a linguistic unit. For example, the contrast between the /p/ and /b/ PHONEMES of English, as in pin v. bin, may be defined in terms of VOICING, muscular TENSION and ASPIRATION; but only one of these features is necessary to specify the contrast involved, and, once this decision has been made (e.g. voicing), the other features would be seen as redundant, in respect of this contrast. Features of sound (grammar, MEANING) which are not considered redundant are DISTINCTIVE. It should be noted that circumstances may arise which will affect the GENERALITY of an analysis; for instance, in other positions in the word, other features may become less redundant (e.g. muscular tension in final position, as in such contrasts as rip v. rib), and in some VARIETIES of speech (such as public speaking, or in very noisy situations) the speaker may need to use all the available features in order to be ACCEPTABLE or intelligible.

Similar principles apply to the analysis of grammar and SEMANTICS in terms of redundancy. In grammar, for example, SENTENCES such as The bird flies display redundancy, in that both the SUBJECT and the VERB are MARKED for singularity: in theory, it would be possible for English to use, for example, the bird fly v. the birds fly to keep a singular/plural distinction clear. In semantics, the issue is more complex: what to one person might appear a totally unnecessary (and hence redundant) use of a word or phrase may to someone else provide an additional nuance, and thus be distinctive.

In GENERATIVE linguistics, the notion of redundancy has been formalized in terms of RULES (redundancy rules) which simplify the form of descriptions. Any feature which can be predicted on the basis of other features is said to be redundant. For example, in generative PHONOLOGY, when certain features of a SEGMENT are predictable (because of the occurrence of other features in some CO-OCCURRING segment), the specification of these features is unnecessary: such redundant feature specifications would be left blank in the UNDERLYING representation of MORPHEMES (the rules subsequently involved in inserting the redundant features being referred to as ‘LEXICAL-redundancy rules’ or MORPHEME STRUCTURE RULES). Redundancy rules are also important in UNDERSPECIFICATION theories of phonology. In generative SYNTAX, the lexical-redundancy rules apply to such processes as SUB-CATEGORIZATION (thus simplifying the feature specification of a syntactic CATEGORY) and WORD-FORMATION (enabling one WORD-CLASS to be DERIVED from another).

Various mathematical methods are available to demonstrate the nature and extent of redundancy in linguistic analysis.