compound-complex sentence

[ kom-pound-kom-pleks ]
/ ˈkɒm paʊndˈkɒm plɛks /
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a sentence having two or more coordinate independent clauses and one or more dependent clauses, as The lightning flashed (independent clause) and the rain fell (independent clause) as he entered the house (dependent clause).
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Origin of compound-complex sentence

First recorded in 1920–25
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022


What is a compound-complex sentence?

A compound-complex sentence is a sentence with two or more independent clauses 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.

Like a compound sentence, a compound-complex sentence has at least two independent clauses. And like a complex sentence, a compound-complex sentence has at least one dependent clause.

In the sentence I went to the party, but Rick couldn’t go with me because he had to babysit. I went to the party and but Rick couldn’t go with me are independent clauses. Each can stand alone as a grammatically complete sentence (a complete thought). Because he had to babysit is a dependent clause. It’s not a complete thought and can’t stand alone.

Why are compound-complex sentences important?

The first records of the phrase compound-complex sentence come from around 1920. It combines the words compound, meaning “composed of two or more parts,” complex, meaning “made of parts,” and sentence, meaning “a grammatical unit of words that expresses an independent idea.” A compound-complex sentence combines aspects of both compound and complex sentences to make an even more complicated sentence.

Compound-complex sentences are the most complicated sentence structure that you can use in English. They are often very long, usually have multiple conjunctions, often have a number of punctuation marks, could have numerous prepositional phrases, and may even use more than one verb tense.

Compound-complex sentences are best used for sharing complicated ideas. However, they can be confusing for a reader or listener, especially if there are several compound-complex sentences in a row. Legal and medical writing often use this sentence structure, which is one reason they’re challenging to understand.

Because they have multiple independent clauses, you can make your writing easier to understand by breaking up compound-complex sentences into multiple sentences. For example:

  • Compound-complex sentence: I tried to rescue the kitten from the tree, but she was scared because she was so high up in the air. 
  • Simple sentence and compound sentence: I tried to rescue the kitten from the tree. Unfortunately, she was scared because she was so high up in the air. 

Did you know ... ?

Compound-complex sentences follow the same grammatical rules as both compound sentences and complex sentences. If compound-complex sentences are giving you trouble, review these other two types of sentences first and apply what you know about them to compound-complex sentences.

What are real-life examples of compound-complex sentences?

This graphic gives an example of a compound-complex sentence and splits it up into its separate clauses.

Compound-complex sentences are common in English, although people may find them tricky to handle.

Quiz yourself!

Is the following sentence an example of a compound-complex sentence?

Whenever I see a majestic falcon, I carefully take a picture of it, but I won’t disturb it as I use my camera.

How to use compound-complex sentence in a sentence

Cultural definitions for compound-complex sentence

compound-complex sentence

A sentence that contains at least two independent clauses and at least one dependent clause: “Queen Elizabeth I was called a redhead (independent clause), but no one knew her hair color for sure (independent clause) because she always wore a wig (dependent clause).” “Because she always wore a wig” is a dependent clause starting with the subordinating conjunction (see subordination) because. (Compare complex sentence, compound 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.