complex sentence

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Definition of complex sentence

a sentence containing one or more dependent clauses in addition to the main clause, as When the bell rings (dependent clause), walk out (main clause).


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Origin of complex sentence

First recorded in 1880–85
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022


What is a complex sentence?

A complex sentence is a sentence with one independent clause and at least one dependent clause.

In grammar, a clause is a group of words that contains a subject and a predicate. The subject is the word that indicates what a sentence is about or who or what is performing an action. A subject can be a noun (car, Tom), a noun phrase (short book, green apples), or a noun substitute (you, they). The predicate is a word that indicates what the subject is doing. A predicate is a verb (runs, is) and the words that govern or modify it (fast, hungry).

An independent clause contains a complete thought and can be used by itself as a sentence, as in It is time for lunch. A dependent clause does not contain a complete thought and can’t be used by itself. It depends on another clause to make sense, as in When the clock strikes noon.

A complex sentence contains both types of clauses, as in When the clock strikes noon, it is time for lunch.

While a complex sentence can have only one independent clause, it can have more than one dependent clause, as in When I was a young man, I was afraid of clowns until a clown rescued my sister. Here, I was afraid of clowns is an independent clause, containing the main idea. When I was a young man and until a clown rescued my sister are dependent clauses that tell you more about the main idea.

Complex sentences are simple sentences plus one or more dependent clauses.

Why are complex sentences important?

The first records of the phrase complex sentence come from around 1880. It combines the words complex, meaning “made of parts,” and sentence, meaning “a grammatical unit of words that expresses an independent idea.” A complex sentence is a sentence made up of two or more parts—an independent clause and at least one dependent clause.

Complex sentences are one type of sentence that helps us share more information about a single main idea, such as conditions related to that main idea, as in I like chocolate unless it has peanuts in it. The dependent clause can go before the main clause, as in If you never try, you will never succeed, or after it, as in Juan returned the book to the library after he finished reading it.

Understanding complex sentences will help you understand similar sentence structures, such as compound sentences and compound-complex sentences.

Did you know ... ?

Almost all complex sentences will have at least one subordinating conjunction that indicates a dependent clause. Some examples of subordinating conjunctions include if, because, when, although, and until.

What are real-life examples of complex sentence?

This graphic defines a complex sentence and gives an example of one.

English Hints


We use complex sentences all the time.


Quiz yourself!

Which of the following is NOT an example of a complex sentence?

A. My dad was a champion skier until he broke his leg.
B. When it rains, my plants are happy.
C. I am the king of the world.
D. Billy will share his toys if Mandy shares her crayons.

How to use complex sentence in a sentence

British Dictionary definitions for complex sentence

complex sentence

grammar a sentence containing at least one main clause and one subordinate clause
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Cultural definitions for complex sentence

complex sentence

A sentence that contains one main clause or independent clause and at least one subordinate clause or dependent clause: “Although I am tired (subordinate clause), I want to go to the midnight movie (main clause).” (See subordination; compare compound sentence, compound-complex sentence, and simple sentence.)

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.