[...] for the purposes of the nominal group we need to take account of just one such relationship, that of subcategorization: ʻ 'a' is a subset of 'x' ʼ. This has usually been referred to in the grammar of the nominal group as MODIFICATION, so we will retain this more familiar term here [...] Here however we are not concerned with the differences but with the similarities: with the general relationship that runs throughout the pre-Head modification of the nominal group, whatever the experential function of the individual elements.
- Halliday (1985), a pag.170