adequacy (n.)

A term used in LINGUISTIC theory as part of the evaluation of levels of success in the writing of GRAMMARS. Several sets of distinctions based on this notion have been made. External adequacy judges a grammar in terms of how well it corresponds to the DATA (which are ‘external’ to the grammar); internal adequacy is a judgement based on the ‘internal’ characteristics of the grammar, such as its SIMPLICITY, elegance, etc. From a different point of view, grammars are said to be weakly adequate if they GENERATE some desired set of SENTENCES; they are strongly adequate if they not only do this but also assign to each sentence the correct STRUCTURAL DESCRIPTION. An alternative formulation recognizes three levels of achievement in grammars: observational adequacy is achieved when a grammar generates all of a particular sample (CORPUS) of data, correctly predicting which sentences are WELL FORMED; descriptive adequacy is achieved when a grammar goes beyond this, and describes the INTUITIONS (COMPETENCE) of the language’s speakers; explanatory adequacy is achieved when a principled basis is established for deciding between alternative grammars, all of which are descriptively adequate. More specifically, an explanatorily adequate grammar will explain why language ACQUISITION in a relatively short period of time is possible on the basis of primary linguistic DATA.