… language has evolved in the service of particular human needs … what is really significant is that this functional principle is carried over and bu… - Michael Halliday

The text is a product in the sense that it is an output, something that can be recorded and studied, having a certain construction that can be represented in systematic terms. It is a process in the sense of a continuous process of semantic choice, a movement through the network of meaning potential, with each set of choices constituting the environment for a further set.

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.

[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.