Linguistics is the name of an academic subject. (For some difficulties in meaning, see linguistic.)
Linguistics is "The science of languages; philology" (OED, s.v. linguistic[ a. and n., B. n. [-IC 2.]). Definitions tend to concentrate on "the scientific" or "systematic" "study of language". The academic subject is indeed a science, and concentrates on the theoretical understanding of human languages, and the practical applications of the theory. Its branches include grammar, or the systematic study of structure; etymology, or the study of the history and origin of words and the languages they compose; phonetics, or the study of the sounds of languages; and semantics, or the study of the meanings of words. Linguists, or linguisticians, study such things as children's acquisition of language, sociolinguistics, and accent and dialect. Their work is of great value to teachers of foreign languages, and indeed of native languages. Amongst much work that is done, some linguists (lexicographers) work on dictionaries, others write grammars, and some try to produce a universal grammar, or an account of the rules that underlie all human languages.