An amorphous and indeterminate set of ʻuses of languageʼ is partly reducible to generalized situation types, the social contexts and behavioural settings in which language functions. For any one of these situations types, we seek to identify a meaning potential, the range of alternatives open to the speaker in the context of that situation type; these are expressed as semantic networks within which meaning selections are made. The options in the semantic network determine the choice of linguistic forms by ʻpre-selectionʼ of particular options within the functional components of the grammar. These grammatical options are realized in integrated structures formed by the mapping on to one another of configurations of elements derived from each the ʻmacro-functionsʼ.
- Halliday (1973), a pag.101

A semantic network is a hypothesis about patterns of meaning, and in order to be valid it must satisfy three requirements. It has to account for the range of alternatives at the semantic stratum itself; and it has to relate these both ʻupwardsʼ, in this instance to categories of some general social theory or theory of behaviour, and ʻdownwardsʼ, to the categories of linguistic form at the stratum of grammar.
- Halliday (1973), a pag.76

[...] the semantic network is an account of how social meanings are expressed in language. It is the linguistic realization of patterns of behaviour.
- Halliday (1973), a pag.79

The behaviour patterns that we derive from social contexts and settings are thus intrinsic to sociological theory; they are arrived at in the search for explanations of social phenomena, and are indipendent of whatever linguistic patterns may be used to express them. The function of the semantic network is to show how these ʻsocial meaningsʼ are organized into linguistic meanings, which are then realized through the different strata of the language system. But whereas the social meanings, or behaviour patterns, are specific to their contexts and settings, their linguistic reflexes are very general categories as those of transitivity, of mood and modality, of time and place, of information structure and the like. The input to the semantic networks is sociological and specific; their output is linguistic and general.
- Halliday (1973), a pag.80

[...] The semantic network is the ʻinputʼ to the grammar. The semantic network forms the bridge between behaviour patterns and linguistic forms.
- Halliday (1973), a pag.83

These networks are what we understand by ʻsemanticsʼ. They constitute a stratum that is intermediate between the social system and the grammatical system. The former is wholly outside language, the latter is wholly within language; the semantic networks, which describe the range of alternative meanings available to the speaker in given social contexts and settings, from a bridge between the two. Like any other level of representation in a stratal pattern, they face both ways. Here, the downwards relation is with grammar; but the upwards relation is with the extra-linguistic context.
- Halliday (1973), a pag.96