“[The construal of context as a semiotic construct accompanies the construal of language as a metafunctionally organized system because of the realizational relationship between the two. And it is this relationship which helps to explain how language is learned:]It is this that enables, and disposes, the child to learn the lexicogrammar: since the system is organized along functional lines, it relates closely to what the child can see language doing as he observes it going on around him.”