complex sentence

A complex sentence is a sentence that contains one independent clause and one or more dependent clauses.

Independent clause

A clause is a word group that contains a subject and a verb.

An independent clause (which is the same as a simple sentence) is a clause that expresses a complete thought and can stand alone. Here is an example:

• My cousin Marjorie returned her iguana to the pet store.

In this clause, the subject is My cousin Marjorie and the verb is returned. The clause makes sense by itself, so it is an independent clause.

Dependent clause

A dependent clause, in contrast, does not make sense by itself; it depends on an independent clause to give it meaning. Here is an example:

• after she saw Godzilla’s Bride

Although this dependent clause contains the subject she and the verb saw, it does not express a complete thought; it must be attached to an independent clause to make sense.

If we add this dependent clause to the independent clause shown above, the two clauses form a complex sentence:

• My cousin Marjorie returned her iguana to the pet store after she saw Godzilla’s Bride.

Role of the dependent clause

In a complex sentence, the dependent clause acts as an adjective, an adverb or a noun.

An adjective clause modifies a noun or pronoun:

• Our newest ringtone is The Jackhammer, which sounds like a drill.  (adjective clause modifies noun Jackhammer)
• I have a prize for the one who gets all the answers right.  (adjective clause modifies pronoun one)

An adverb clause modifies the verb and answers questions like when, where, why or how:

• Jason watched an exercise program because he wanted to tone up.  (adverb clause tells why he watched the program)

A noun clause acts as a noun and can do anything a noun can do; for example, it can be the subject or object of a verb.

• What you heard is untrue.  (noun clause is subject of verb is)
• Lise heard that bok choy would be on sale at The Broccoli Barn.  (noun clause is object of verb heard)

Position of the dependent clause

The dependent clause is often at the end of the sentence, as most of the examples above show. But it can also be at the beginning:

• Before I arrived in Canada, I had never seen a moose.  (introductory adverb clause)
• Whoever leaves last should turn off the lights.  (noun clause, subject)

Or in the middle:

• The friend who made me this bracelet creates her own designs.  (adjective clause)
• Sam and Jessica, once they had finished packing, went out for a meal.  (adverb clause)

An easy way to add variety to your writing is to position dependent clauses in different places in the sentence.

Commas with dependent clauses

As you can see from the above examples, the use of commas with dependent clauses varies according to the type of clause and its position in the sentence. For detailed information on how to use commas with dependent clauses, read the Writing Tips ADJECTIVE CLAUSE, ADVERB CLAUSE and NOUN CLAUSE.

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