If something is said to be metaphorical, there must be something that is not; and the assumption is that to any metaphorical expression corresponds another, or perhaps more than one, that is ʻliteralʼ -- or, as we shall prefer to call it, CONGRUENT. In other words, for any given semantic configuration there is (at least) one congruent realization in the lexicogrammar. There may then be others that are in some respect transferred, or METAPHORICAL.
- Halliday (1985), a pag.321

A congruent expression is one in which this direct line of form to meaning to experience is mantained intact, as it is in young children's language like 'man clean car'.
- Halliday (1985), a pag.XIX