Language structure and language function - статья на английском языке

Why is language as it is? The nature of language is closely related to the demands that we make on it the functions it has to serve. <...>
It is fairly obvious that language is used to serve a variety of different needs, but until we examine its grammar there is no clear reason for classifying its uses in any particular way. However, when we examine the meaning potential of language itself, we find that the vast numbers of options embodied in it combine into a very few relatively independent 'networks'; and these networks of options correspond to certain basic functions of language. This enables us to give an account of the different functions of language that is relevant to the general understanding of linguistic structure rather than to any particular psychological or sociological investigation.
1. Language serves for the expression of 'content': that is, of the speaker's experience of the real world, including the inner world of his own consciousness. We may call this the ideational function, though it may be understood as easily in behavioural as in conceptual terms. In serving this function, language also gives structure to experience, and helps to determine our way of looking at things, so that it requires some intellectual effort to see them in any other way than that which our language suggests to us.
2. Language serves to establish and maintain social relations: for the expression of social roles, which include the communication roles created by language itself - for example the roles of questioner or respondent, which we take on by asking or answering a question; and also for getting things done, by means of the interaction between one person and another. Through this function, which we may refer to as interpersonal, social groups are delimited, and the individual is identified and reinforced, since by enabling him to interact with others language also serves in the expression and development of his own personality. <...>
3. Finally, language has to provide for making links with itself and with features of the situation in which it is used. We may call this the textual function, since this is what enables the speaker or writer to construct 'texts', or connected passages of discourse that is situationally relevant; and enables the listener or reader to distinguish a text from a random set of sentences.
(From "New Horizons in Linguistics", "Language Structure and Language Function" by M. A. K. Halliday)