Redundancy (linguistics)

In linguistics, redundancy refers to information that is expressed more than once.

Examples of redundancies include multiple agreement features in morphology, multiple features distinguishing phonemes in phonology, or the use of multiple words to express a single idea in rhetoric.

Redundancy may occur at any level of grammar. Because of agreement – a requirement in many languages that the form of different words in a phrase or clause correspond with one another – the same semantic information may be marked several times. In the Spanish phrase los árboles verdes ("the green trees"), for example, the article los, the noun árboles, and the adjective verdes are all inflected to show that the phrase is plural. An English example would be: that man is a soldier versus those men are soldiers.

In phonology, a minimal pair is a pair of words or phrases that differs by only one phoneme, the smallest distinctive unit of the sound system. Even so, phonemes may differ on several phonetic features. For example, the English phonemes /p/ and /b/ in the words pin and bin feature different voicing, aspiration, and muscular tension. Any one of these features is sufficient to differentiate /p/ from /b/ in English.

Generative grammar uses such redundancy to simplify the form of grammatical description. Any feature that can be predicted on the basis of other features (such as aspiration on the basis of voicing) need not be indicated in the grammatical rule. Features that are not redundant and therefore must be indicated by rule are called distinctive features.

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