Composite sentences
So far we have discussed relatively simple sentences involving a single finite verb. We can also identify other constructions in which there are two or more sentences or sentence fragments including a finite verb (i.e. clauses). In some cases, these are straightforwardly conjoined and of equal status:
John read the paper and Peter mowed the lawn.
Either the dog goes or I go.
Such sentences are known as compound sentences. Either of the two conjoined sentences within these two examples could function independently and there is no sense in which one is dependent on the other. On the other hand, in the following examples, one of the clauses is independent and would stand alone, while the other, in bold, is an a sense secondary or subordinate:
1 Steve knew that his time was up.
2 Peter, who had never seen a gun before, froze to the spot.
3 Jenny and Julie texted each other while the band played Rule Britannia.
Sentences with at least one dependent or subordinate clause are known as complex sentences. In sentence 1, the subordinate clause is a complement of the verb knew, and fills a slot that might easily be taken up with an NP (e.g. Julie, his place, the reason for his failure). In sentence 2 the clause modifies, or relates to, a single constituent in the sentence, i.e. Peter, and is known as a relative clause. Finally, the clause in sentence 3 is an adjunct, giving additional information about the manner in which the action described in the main clause took place: it could easily be replaced in this frame by an adverb or adverbial phrase (e.g. frantically, expertly, all day, out of boredom).
Relative clauses are used to modify nouns within the main clause, and thereby qualify them in the way that an adjective would (hence the term ‘adjectival clause’ from traditional grammar): they are introduced by relative pronouns such as which, where, when or, as in sentence 2, who. We need to distinguish two kinds of relative clause:
restrictive relative clauses provide essential information about the noun to which they refer
non-restrictive relative clauses are adjuncts, providing additional information about the noun in question.
Compound sentences are linked by co-ordinating conjunctions or co-ordinators. In English these include and, or (either on its own or in the combination either… or), for, but and yet. Complex sentences, however, are conjoined in a variety of ways: the subordinate clause is introduced in sentence 1 above by the subordinating conjunction (or subordinator) that; in sentence 2 by a relative pronoun (who); and in sentence 3 by a temporal subordinator (while).
