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

Modern linguistics is mostly prescriptive, but sometimes descriptive.

A diachronic study of language is the description of language at some point in time.

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

Social changes can often bring about language changes.

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.

Syntax

General linguistics, which relates itself to the research of other areas, studies the basic concepts, theories, descriptions, models and methods applicable in any linguistic study.

In the study of linguistics, hypotheses formed should be based on language facts and checked against the observed facts.