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.

Modern linguistics is mostly prescriptive, but sometimes descriptive.

Pragmatics

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

Sociolinguistics is the study of language in relation to society.

Social changes can often bring about language changes.

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

Findings in linguistic studies can often be applied to the settlement of some practical problems. The study of such applications is generally known as a（）linguistics.

Morphology studies how words can be formed to produce meaningful sentences.

Langue refers to the a（）linguistic system shared by all the members of a speech community while the parole is the concrete use of the conventions and application of the rules.