layer theme, a new concept in functionalism

abstract: the research at hand discusses about the notion of the theme in persian scientific and literary genres from the point of view of halliday’s systemic functional grammar (sfg) and explains and determines the similarities and differences of the two genres in persian language. in this research, after mentioning the obvious differences of the two genres from the point of view of theme type and its frequency, types of clauses and their relationship with the theme have also been studied and structural features of clauses are compared regarding the two genres. during data analysis, theme position in the clauses and its overlap in the form of intertwined layers, have led to the introduction of the of layer theme for the first time. this specialized term, is important and remarkable in functional researches. layer theme exists when themes of the complex clauses have simultaneous overlap in terms of constitutive levels or layers.