Halliday & Matthiessen (1999: 102):
These special subcategories have the effect of construing other elements as “referable” — that is, of enabling them to retain their semiotic identity for subsequent access and hence as it were authenticating them (e.g. Don’t give me any more of that peanut butter! I can’t stand the stuff.) This applies primarily, though not exclusively, to participants. At the same time, it allows us to recognise not only of the ‘simple’ type but also ‘larger’ elements known as macro- and meta-phenomena. Macro-phenomena are figures downranked to function as ordinary elements; meta-phenomena are figures projected as elements of a second order.