Halliday & Matthiessen (1999: 76-7):
Stephen's definition of 'balance' is on a developmental path towards the kinds of definition used in educational and scientific discourse — definitions such as the dictionary definition of 'cat': a cat is a carnivorous mammal long domesticated and kept by man as a pet or for catching rats and mice… . The definition of 'cat' involves a move to a less delicate category ('carnivore' or 'carnivorous mammal', which can be reconstrued as 'mammal that eats meat' …) plus a qualification by a downranked sequence of figures of doing: see Figure 2-12.
In both examples, the definition construes a token-value relation between a fairly delicate semantic type that is lexicalised within the lexicogrammar and a restatement of this type by means of other resources in the ideation base. The restatement draws more on the resources towards the grammatical end of the scale, so that in the definition a lexicalised token is construed as a grammaticalised value.
This entails a shift from construing experience through depth in the experiential taxonomy towards construing experience through expansion in a logical sequence. In the first example, this only involves a downranked sequence of figures; in the second example, this involves a move towards a less delicate category plus a downranked sequence of figures. The first example can actually be interpreted as meaning 'the condition when you hold it on your fingers and it doesn't fall off', showing that the downranked sequence has the class meaning of 'condition'.