Every process has associated with it one participant that is the key figure in that process; this is the one through which the process is actualised, and without which there would be no process at all. Let us call this element the Medium, since it is the entity through the medium of which the process comes into existence. … in a material process the Medium is equivalent to the Actor in an intransitive clause and Goal in a transitive clause.
Monday, 30 April 2012
The Medium [Definition]
Halliday & Matthiessen (2004: 288-9):