Halliday & Matthiessen (1999: 87, 88):
In general, then, we can say that the move in delicacy in the ideation base from 'most general' to 'most delicate' is construed lexicogrammatically as the move from 'grammar' to 'lexis': see Figure 2-15.
This is of fundamental significance in the construal of semantic categories. The early part of the scale of delicacy is construed in the grammatical 'zone'. This zone provides the resources of grammatical schematisation for construing more delicate categories: those categories are realised lexically but construed according to the systemic parameters of the grammar. For example, the grammar of the nominal group provides a schema for construing various delicate categories of things, by classifying, describing, ordering and other such strategies.