Halliday & Matthiessen (1999: 14):
The distinction between paradigmatic organisation and syntagmatic organisation opens up one dimension of the ideation base. As we have said, syntagmatic specifications occur in paradigmatic environments, as realisations of paradigmatic types. But the global organisation of the ideation base is paradigmatic; the paradigmatic network is ordered in delicacy (subsumption, classification, specialisation), from the least delicate (most general) to the most delicate (most specific types).