In the relative orientation of different social groups towards the various functions of language in given contexts and towards the different areas of… - Michael Halliday

[A register is constituted by] the linguistic features which are typically associated with a configuration of situational features - with particular values of the field, mode and tenor.

[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.

Language... is a range of possibilities, and an open end set of options in behavior that are available to the individual in his existence as social man. The context of culture is the environment of any particular selection that is made within them... The context of culture defines the potential, the range of possibilities that are open. The actual choice among these possibilities takes place within a given context of situation.