Special Theme constructions refer to such constructions as cleft, pseudo-cleft, it-extraposition, existential sentence; and detachment which are characterized by their non-canonical syntactic features in Theme. These constructions have been treated within both traditional and functional grammar, where they are mostly described and explained in terms of information structure, sometimes with reference to their discourse functions. These descriptions and explanations can be subsumed under the heading of textural function of the clause, which, according to systemic functional linguistics, includes...
