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:

  • When you leave, please lock the door. (adverb clause tells when you should lock the door)
  • Since winning the lottery, Mandeep can vacation wherever he chooses. (adverb clause tells where Mandeep can vacation)
  • Because Jason wanted to tone up, he watched an exercise program. (adverb clause tells why Jason watched the program)
  • Karla ran as if her life depended on it. (adverb clause tells how Karla ran)

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 discovered that bok choy would be on sale at The Broccoli Barn. (noun clause is object of verb “discovered”)

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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A tool created and made available online by the Translation Bureau, Public Services and Procurement Canada

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