The complex sentence with nominal clauses 617
§ 149. All nominal clauses have a function approximating to that of a noun or a nominal phrase. They may fulfil the function of a basic part of the main clause: a subject clause functions as subject of the main clause which has no subject of its own, a predicative clause functions as predicative to the link verb within the main clause; an object clause refers to verbs in different forms and functions, to adjectives, statives and occasionally to nouns, and may be obligatory or optional. Another type of the nominal clause - an appositive clause, refers to a noun either with a very general meaning or requiring additional information and is therefore essential to the meaning of the sentence.
Owing to their essential structural and semantic role in the sentence, all nominal clauses are very closely connected with the main clause, and if such a clause is removed, both the structure and meaning of the sentence are changed or become ungrammatical. Because of the close relationship between the clauses the complex sentence is pronounced as one whole, and the subordinate clause is not commad off, unless it is much extended and contains constructions or detached parts.
Since nominal clauses function as essential structural parts of the sentence, their relations to the main clause are confined to such purely grammatical sentential relations as subjective, predicative, objective and appositive.