Halliday & Matthiessen (2014: 290):
In the ‘circumstantial’ type, the relationship between the two terms is one of time, place, manner, cause, accompaniment, role, matter or angle. These are also manifested as circumstantial elements in the English clause.
As manifestations of the 'fractal types', the relationship is one of
- enhancement (time, place, manner, cause),
- extension (accompaniment),
- elaboration (role), or
- projection (matter, angle).