Distinguishing First Order Field And Second Order Field

Halliday & Matthiessen (1999: 321-2):

… field can be characterised as the deployment and organisation of the ideation base. … there are two aspects to this category. In most contexts, there is both a first order field and a second order field — the first order field is the social activity being pursued (eg instructing somebody in how to prepare a dish …) and the second order field is the ‘subject matter’ the activity is concerned with (eg the ingredients and methods of cooking …). … And both these guide the way the ideation base is deployed.