The aim of this study is to investigate the function and use of English complementizers ‘that and for’ and to examine how these complementizers interact with(in) the semantic scope of complex sentences. The study argues that the transformational processes of English complementizers have the potential to change and manipulate the sentence/speaker's meaning. This manipulative change of meaning is firstly abode by the complementizer used within the matrix of (complex) sentence and secondly by the type that the propositional content of the sentence refers to (whether the information conveyed expresses objective knowledge, subjective mood, moral judgment, emotional state or open, uncertain question). The study concludes that the classification of verbs plays an essential role in selecting the complementizer to be properly used in covering the necessary cognitive status of the sentence at the syntactic and semantic levels. Thus, each complementizer has its own semantic restrictions, which differentiate it from other complementizers.