Are you wondering what are compound sentences? Learn more in this guide!

One of the topics you probably learned about in high school or earlier is the types of sentences available to use in the English language. If you’re wondering, what are compound sentences again, you’re not alone. These Sentence types trip up many people.

A compound sentence joins together two separate but related complete thoughts, called independent clauses, into a single sentence. Compound sentences are very common in English grammar usage, but implementing them properly takes a bit of practice. Here’s what you need to know.

What Are Compound Sentences? A Definition

Compound sentences are sentences with more than one independent clause, properly joined together with either a semicolon or a comma and a conjunction. To qualify as a compound sentence, a sentence must have at least two sets of subjects and verbs paired together as part of English grammar clauses that could stand alone.

Here are some examples of compound sentences.

• Coffee is a popular beverage to start the day, and it may have some health benefits.
• Coffee is popular, but tea is more healthful.
• I had no plans for lunch today, so Sheila invited me to eat with her.

Both halves of that sentence are complete thoughts and could be complete sentences. But since they are related ideas, it makes sense to connect them.

Understanding compound sentences requires understanding other sentence types and the components that make up those sentences.

What Are the Other Types of Sentences?

There are three other types of sentences that you’ll use in writing along with compound sentences, for a total of four sentence types.

In English, you can choose from simple sentences, compound sentences, complex sentences, and compound-complex sentences. 

Simple Sentences

Simple sentences have only one independent clause. This independent clause can have a single subject and verb, or it can have multiple subjects and verbs, but there will only be one clause.

• I went to the store.
• Sheila and I met up for lunch.
• Sheila and I prepared and ate lunch together.

Complex Sentences

Complex sentences have at least one dependent clause and one independent clause. A dependent clause is a part of a sentence containing a subject and a verb pair but that cannot stand on its own (independently).

• If you want to join me for lunch, I need to go to the store.

In that example, the first half of the sentence, “If you want to join me for lunch,” has a subject and a verb, but it cannot stand on its own. It is a dependent or subordinate clause. But “I need to go to the store” could stand on its own, so it is an independent clause.

Compound-Complex Sentences

Compound-complex sentences contain at least two independent clauses and at least one dependent clause. These sentences are longer and more complicated. Depending on how you build the sentence, the clauses could come in any order.

·No matter what happened yesterday, Sheila was coming for lunch, and I had to go to the store first.

What Are Coordinating Conjunctions?

There are seven standard coordinating conjunctions in English: for, and, nor, but, or, yet, and so. When writing a compound sentence, the easiest way to do so is to join two independent clauses with a comma and one of these conjunctions.

Look at the word following the comma in each of these example sentences.

• Writers often use compound sentences, but they must remember to use a comma and coordinating conjunction.
• It was a dark and stormy night, so I decided to stay in.
• Dogs like to go on walks, and dog owners benefit from the exercise, too.

If you need help remembering what the coordinating conjunctions are, use the acronym FANBOYS as a mnemonic device, or memory aid.

Are There Other Ways To Write A Compound Sentence?

Yes, there are two other appropriate ways to write a compound sentence. First, you can join two independent clauses with a semicolon and leave out the coordinating conjunction. This method typically implies a heavier pause between the clauses (when read or spoken).

• It’s getting close to lunchtime; I should decide where to eat.

Some sentences work better with a semicolon, such as when none of the coordinating conjunctions communicates the right sense of connection or causality. Many compound sentences are acceptable either way, with only slight shades of meaning between the two methods.

• A new lamp can freshen up your workspace, and you’ll enjoy having more light, too.
• A new lamp can freshen up your workspace; you’ll enjoy having more light, too.

You can also separate the two clauses of a compound sentence with a colon, especially if you want the reader to look ahead. The two clauses should be tightly connected, with a clear sense that the second follows the first. Be careful not to overuse this technique, though: too many such colons can create confusion and sound amateurish.

Here’s an example of a compound sentence joined with a colon.

·The new office complex looked expensive: the exterior gleamed in polished metal or glass.

Common Mistakes When Writing Compound Sentences

Avoid these common writing mistakes when producing compound sentences. First, a comma splice is when you join two independent clauses with a comma, but you forget the coordinating conjunction. This is a grammatical error and should be avoided.

Comma Splice

The following sentence contains three independent clauses, all spliced together with commas.

• Sheila and I met for lunch, she’s a great friend, I love her.

You could take several approaches to fix this mess, including these.

• Sheila and I met for lunch. She’s a great friend; I love her.
• Sheila and I met for lunch, for she’s a great friend; I love her.

Of course, in the real world, you’d probably want to rework that sentence beyond the suggestions given here.

Need help? Read our guide to comma placement checkers.

Run-on

A run-on is a compound sentence where the predicate of the first clause runs headlong into the subject of the next one with nothing in between.

·The new office complex looks expensive it’s tall I want to go inside.

Make sure to avoid run-ons in your writing. Each distinct thought needs its own treatment, either as its own separate sentence or with proper punctuation and conjunctions.

Fragment

A sentence fragment occurs when you use only a subject or only a predicate and fail to join the two.

• Linking the various portions of a sentence with proper punctuation.
• The scientists, who were all agreed about the results of the study.

These examples don’t express complete thoughts. The first omits the subject, while the second omits the verb or predicate.

If you’re tripping up on sentence fragments and run-ons, here’s a resource that explores these concepts in greater detail.

Final Word on What Are Compound Sentences

Using compound sentences properly is an indispensable part of writing well in the English language. Remember to join the two clauses properly, and make sure to vary sentence types throughout a passage, too. You don’t want all the sentences to look and sound the same. 

FAQs About What Are Compound Sentences