described systems such as mood, agency, theme, etc. Halliday describes grammatical systems as closed, i.e. as having a finite set of options. By contrast, lexical sets are open systems, since new words come into a language all the time. These grammatical systems play a role in the construal of meanings of different kinds. This is the basis of Halliday's claim that language is meta-functionally organised. He argues that the raison d'être of language is meaning in social life, and for this reason all languages have three kinds of semantic components. All languages have resources for construing experience (the ideational component), resources for enacting humans' diverse and complex social relations (the interpersonal component), and resources for enabling these two kinds of meanings to come together in coherent text (the textual function). Each of the grammatical systems proposed by Halliday are related to these metafunctions. For instance, the grammatical system of 'mood' is considered to be centrally related to the expression of interpersonal meanings, 'process type' to the expression of experiential meanings, and 'theme' to the expression of textual meanings. Traditionally the "choices" are viewed in terms of either the content or the structure of the language used. In SFG, language is analysed in three ways (strata): semantics, phonology, and lexicogrammar. SFG presents a view of language in terms of both structure (grammar) and words (lexis). The term "lexicogrammar" describes this combined approach. Metafunctions From early on in his account of language, Halliday has argued that it is inherently functional. His early papers on the grammar of English make reference to the "functional components" of language, as "generalized uses of language, which, since they seem to determine the nature of the language system, require to be incorporated into our account of that system." Halliday argues that this functional organization of language "determines the form taken by grammatical structure". Halliday refers to his functions of language as metafunctions. He proposes three general functions: the ideational, the interpersonal and the textual. Ideational metafunction The ideational metafunction is the function for construing human experience. It is the means by which we make sense of "reality". Halliday divides the ideational into the logical and the experiential metafunctions. The logical metafunction refers to the grammatical resources for building up grammatical units into complexes, for instance, for combining two or more clauses into a clause complex. The experiential function refers to the grammatical resources involved in construing the