As soon as one tries to learn a language，one comes up against the most fundamental questions about the nature of language.What is language？How should one set about learning a language？What is the best way of dividing up this enormous task and or arranging the various features that one recognizes as parts of a language？One cannot teach or learn a language for long without being faced with some of the great puzzles about the nature of language that have baffled the great thinkerssince antiquity.Even the youngest pupil may sometimes present his reader with the most profound issues.How long will it take us to learn the whole language？Are all the words in the dictionary？Why are there so many exceptions？The theory of language with which the teacher operates may not be consciously formulated；it may simply be implicit in the teaching traditions，in the concepts employed to talk about languages，in the way textbooks are arranged，or in the content and format of dictionaries and grammars；but it is hardly imaginable that a language could be taught without some underlying conception of the general nature of language.

It is Linguistics which constitutes the most systematic study of language at our disposal.The obvious reason，then for considerable role of linguistics in relation to foreign language teaching is that both in different ways have to do with language.It would be unreasonable for language teaching theory to disregard what linguistics has to say about language.