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

Phonology

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.

Both semantics and pragmatics study meanings.

Pragmatics is different from semantics in that pragmatics studies meaning not in isolation, but in context.

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

General linguistics is generally the study of language as a whole.

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.

Sociolinguistics is the study of language in relation to society.

The study of the ways in which morphemes can be combined to form words is called morphology.