H. believes that 'the nature of language is closely related to the demands that we make on it, the functions it has to serve'. In this article he briefly discusses that relationship. He distinguishes three functions of language: (i) the 'ideational function', which is usually referred to as the expression of 'content' or 'cognitive meaning' (under this heading he discusses 'transitivity', i.e. the expression of processes and of the participants and circumstances associated with them; here he makes use of a number of notions from case grammar): (ii) the 'interpersonal' function, i.e. the expression of communication roles such as questioner, respondent, etc. (in which connection H. treats the linguistic notion of 'mood'); (iii) the 'textual' function, i.e. the linking of utterances to each other and to the situation (here H. makes use of the concepts 'theme', 'rheme', 'given information', 'new information').