Halliday & Matthiessen (1999: 604n):
Thus semantics, as a field of study, is located within linguistics. We should therefore make it clear that it is not being used in the traditional sense that it has had within linguistics, of the study of the meanings of words. It is used in the sense it has always had in systemic theory, namely the total meaning-making system of a natural language. Semantics thus relates to the lexicogrammar as a whole. We can talk of "lexical semantics" if we want to foreground the meanings of words (lexical items functioning in open sets), and of "grammatical semantics" if we want to foreground the meanings of closed grammatical systems; but just as the lexicogrammar itself is a continuum, so — even more so, in fact — is there continuity between these two aspects of semantics, so we have not found it necessary, except in one or two instances, to make this terminological distinction.