Complex sentences

Like compound sentences, complex sentences consist of at least two clauses. However, the distinction between the two categories lies in the fact that compound sentences contain two (or more) main clauses, while complex sentences contain a main clause and at least one subordinate clause.

John rode the bicycle that his parents had given him for his birthday.

In this example, the words his parents had given him for his birthday could not stand as a sentence on their own and therefore they cannot be a main clause. To put it another way, they are dependent upon, or subordinate to, the main clause. At a functional level, they provide the reader with more information about the topic that is the subject of the main clause.

Subordinate clauses are introduced by a sub-group of words known – for obvious reasons – as subordinating conjunctions. The most common examples include:

As a footnote to this list, it must be said that if you read more detailed discussions of grammar than we have space for here, you may well find extensive discussion of the uses of that and which. For our purposes, however, we need say no more than that, in practice, they are both widely used interchangeably as subordinating conjunctions. (Try seeing how the grammar-check on your word-processing programme treats these two words. You may well find that it wants you to use that much more often than which. There is nothing intrinsically wrong with this, but if writing is to be more than a mere mechanical exercise, and provided the basic conventions are respected, some scope for individuality is a good thing.)