productivity (n.)

A general term used in LINGUISTICS to refer to the CREATIVE capacity of LANGUAGE users to produce and understand an indefinitely large number of SENTENCES. It contrasts particularly with the unproductive communication systems of animals, and in this context is seen by some linguists as one of the design features of human language. The term is also used in a more restricted sense with reference to the use made by a language of a specific feature or pattern. A pattern is productive if it is repeatedly used in language to produce further instances of the same type (e.g. the past-TENSE AFFIX -ed in English is productive, in that any new VERB will be automatically assigned this past-tense form). Non-productive (or unproductive) patterns lack any such potential; e.g. the change from mouse to mice is not a productive plural formation – new NOUNS would not adopt it, but would use instead the productive s-ending pattern. Semi-productive forms are those where there is a limited or occasional creativity, as when a PREFIX such as un- is sometimes, but not universally, applied to words to form their opposites, e.g. happy ⇒ unhappy, but not sad ⇒ *unsad.