Linguistics is generally defined as the s（）study of language.

Social changes can often bring about language changes.

D（）is one of the design features of human language which refers to the phenomenon that language consists of two levels: a lower level of meaningless individual sounds and a higher level of meaningful units.

Morphology

The distinction between competence and performance was proposed by F. de Saussure.

The discipline that studies the rules governing the formation of words into permissible sentences in languages is called s（）

Modern linguistics is mostly prescriptive, but sometimes descriptive.

Both semantics and pragmatics study meanings.

P （）refers to the realization of langue in actual use.

A scientific study of language is based on what the linguist thinks.