Halliday & Matthiessen (1999: 28):
A functional grammatics thus allows us to approach semantics from a deeper and more wide-angled perspective. To this general property, systemic functional grammar adds another characteristic— its paradigmatic orientation. For instance, while more formally oriented accounts may approach transitivity patterns essentially in terms of sequences of grammatical classes such as 'nominal group + verb (+ nominal group)' and speak of classes of verb followed by one nominal group ('mono-transitive') or two nominal groups ('di-transitive'), a systemic grammar interprets such sequences in terms of systems of distinct and contrasting process types.