Predicative clauses perform the function of a predicative. The peculiarity of complex sentences with a predicative clause is that in the principal clause we find only part of the predicate, i.e. a link verb, which together with the predicative clause forms a compound nominal predicate.
A predicative clause may be introduced by conjunctions that, whether, whether... or, as, as if, as though, because, lest, the way, or connectives. The latter may be conjunctive pronouns who, whoever, what, whatever, which or conjunctive adverbs where, wherever, when, whenever, how, why, or asyndetically.
The fact was that he had forgotten about it.
The only reason for my coining is because I hoped to see you again.
Our fear was lest we should miss him in the crowd.
That’s what he wants you to think.
The choice of conjunction is closely connected with the meaning of the word functioning as the subject of the main clause. Thus the conjunction because is used when the word functioning as subject expresses reason, the conjunction whether — when it expresses doubtor implies choice. The connective when is used when the noun functioning as subject expresses a temporal notion (time, day, evening, moment) and the connective where is used when it denotes a place. Thus in the sentence given above The only reason for my coming is because I hoped to see you again the meaning of the subject reason predetermines the use of the conjunction because. In the same way in the sentence The question is whether we can manage without him the meaning of the subject question predetermines the conjunction whether.
This, however, does not mean that a certain conjunction is the only possible one, and that no other can be used after a certain word functioning as subject.
If the subject denotes order, proposal, request, suggestion, arrangement, desire,etc., the conjunction that is generally used, followed by a clause with the predicate in the subjunctive mood (should + infinitive).
The regulation was that the first examination should be done in writing.
Our proposal is that you should join in.
Their suggestion was that no one should interfere.
Predicative clauses withcomparative meaning are introduced by the comparative conjunctions as, as if, as though.
It was as though our last meeting was forgotten.
Everything remained as it used to be in this room.
She looks as if she were ill.
Predicative clauses may occur as parts of two structurally different kinds of sentences:
1. They may follow the main clause in which the subject is a notional word, although it usually has a very general meaning (thing, question, problem, news, sensation, evil, rule, trouble, etc.). In this case the predicative clause discloses the meaning of the subject.
Therule was that they walked down to the cliff path and travelled up in the lift.
Thetrouble was whether we could manage it ourselves or not.
Theproblem is not who will go, but who will stay.
2. The predicative clause may follow the main clause in which the subject is expressed by theimpersonal pronoun it. In this case the predicative clause describes the situation, either directly or by means of comparison. The most frequent link verbs used in this pattern are feel, to look, to see; less frequent are to appear, to remain, to become, to sound, to taste.
It appears he hasn’t been there.
It sounded as if even the spring began by act of Parliament.
As a rule predicative clauses are not separated by a comma; a comma is used if we have two or more predicative clauses coordinated with each other.
But the chief reason is, that Mirah will desire to watch over you and that you ought to give her the guardianship of a brother's presence.