What is a compound sentence?

When you’re learning the basic grammatical rules, a helpful place to start is with the four major types of sentences—simple, compound, complex, and compound-complex. By combining clauses and simple sentences, you can form a compound sentence—learn how below.

What is a compound sentence?

To understand a compound sentence, it helps to go back and understand a simple sentence—the first of four types of sentences that form the foundations of writing. A clause is when a subject and a verb are connected and usually functions as a standalone sentence. This is known as both an independent clause and a simple sentence. Here are two examples of simple sentences:

I drank coffee.
Steve drank a soda.

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These two independent clauses both feature a subject, a verb, and a relationship between the two. With proper punctuation ending in a period, they are short sentences that stand on their own and make grammatical sense. When you join these two independent clauses or sentences with a conjunction or punctuation, the unified result is known as a compound sentence.

I drank coffee while Steve drank a soda.
I drank coffee and Steve drank a soda.
I drank coffee but Steve drank a soda.

All three examples above are compound sentences, and while they slightly differ in meaning and intent, they are all joined by conjunctions. These connecting conjunctions can include the following:

And
Or
But
So
Yet
While
When

Independent clauses can also be connected with punctuation, as in the following:

I drank coffee; Steve drank a soda.

Without a connecting conjunction, the semicolon is the most common way to link two sentences that are grammatically independent on their own.

Compound sentence examples

The following are all examples of compound sentences, connected in different ways:

I love painting, but she prefers photography.
I’ll arrive soon when the clock strikes five.
Tony wanted to go out; I wanted to stay home.

“You already understand that an independent clause is one that can stand alone as a grammatically correct sentence; conversely, a dependent clause is a sentence fragment.”

What is a compound-complex sentence?

A complex sentence is another one of the four types of sentences, and it’s made up of an independent and a dependent clause joined together. You already understand that an independent clause is one that can stand alone as a grammatically correct sentence; conversely, a dependent clause is a sentence fragment. Combining the two creates a complex sentence:

Dependent clause: When I grow up
Independent clause: I’m going to be an astronaut
Complex sentence: When I grow up, I’m going to be an astronaut.

A compound-complex sentence joins these two sentence types into a cohesive idea, complete with multiple independent and dependent clauses, as well as a conjunction. Essentially, a grammatically correct compound-complex sentence adds a third thought to a compound sentence:

When I grow up, I’m going to be an astronaut, so I’m going to apply to engineering school.

Compound-complex sentence examples

Many compound-complex sentences use the if-then structure, where it discusses a hypothetical scenario. If both statements are true, then the sentence is true, and vice versa. Here are some examples:

Last night’s basketball game was sold out because it was the playoffs, but some lucky fans managed to buy tickets.
Though Angie prefers watching comedies, she rented the latest action movie and loved it.
If you rarely practice your scales, then you’ll never succeed at playing piano.

It might be difficult at first to wrap your mind around these increasingly complex sentences (from simple to complex to compound-complex, for example!). But once you practice identifying clauses, and identifying the differences between independent and dependent ones, then you’ll understand this essential component of grammar. Check out more writing tips to enhance and streamline your work, such as brushing up on nouns, writing in the passive voice, and adding playfulness to your text with onomatopoeia.