Halliday & Matthiessen (2004: 371-2):
Although groups are word complexes, they cannot be fully accounted for as complexes. Groups have developed their own multivariate constituent structures with functional configurations such as the Deictic + Numerative + Epithet + Classifier + Thing of the nominal group in English. Here the elements are
- (i) distinct in function,
- (ii) realised by distinct classes, and
- (iii) more or less fixed in sequence.
A configuration of such a kind has to be represented as a multivariate structure. Treating the group simply as a ‘word complex’ does not account for all these various aspects of its meaning. It is for this reason that we recognise the group as a distinct rank in the grammar.