The London school

žMichael Halliday (1925)

His first major work on the subject of grammar was "Categories of the theory of grammar",  In this paper, he argued for four "fundamental categories" for the theory of grammar:"unit", "structure", "class" and "system". These categories he argued were "of the highest order of abstraction", but were defended as those necessary to "make possible a coherent account of what grammar is and of its place in language"  In articulating the category 'unit', Halliday proposed the notion of a 'rank scale'. The units of grammar formed a "hierarchy", a scale from "largest" to "smallest" which he proposed as: "sentence", "clause", "group/phrase", "word" and "morpheme".Halliday defined structure as "likeness between events in successivity" and as "an arrangement of elements ordered in places'. Halliday rejects a view of structure as "strings of classes, such as nominal group + verbalgroup + nominal group" among which there is just a kind of mechanical solidarity" describing it instead as "configurations of functions, where the solidarity is organic."