Martin (1992: 301-2):
One further category that needs to be brought in here is antonymy. Whereas synonyms are co-hyponyms for which differences in meaning may not matter, antonyms are co-hyponyms for which they must — because the items in question are opposed in meaning rather than complementing each other;
 Definitionally, synonyms are not types (hyponyms) of co-hyponyms. In SFL theory, synonymy is a lexical means of creating cohesion in discourse.
 Definitionally, antonyms are not types (hyponyms) of co-hyponyms. In SFL theory, antonymy is a lexical means of creating cohesion in discourse.
 Complementing is most generally concerned with completion, and often involves not just opposites (e.g. art: complementary colours), but contradiction (e.g. physics: particle-wave-field). Halliday (2008: 84):
In the most general sense, complementarity is a special form of complexity; one can think of it perhaps as the management of contradiction.