A compound sentence is a sentence that connects two independent clauses, typically with a coordinating conjunction like and or but. It is best for combining two or more sentences that are self-sufficient but related into a single, unified one.
Compound sentences give your writing a faster pace and unite related ideas, but they have a few more rules than standard sentences. In this quick guide, we explain how to use them properly to give your writing an edge.
What is a compound sentence?
As we mention in our guide on how to write better sentences, compound sentences combine two or more independent clauses. The key here is independent clauses, which are clauses that can each stand alone as a separate sentence. Essentially, a compound sentence brings together individual, related sentences as one.
(If you’re unfamiliar with these terms, please check out our guide to clauses in English, which better defines what constitutes a clause.)
Compound sentences are easy to identify because they usually use a coordinating conjunction, which you may remember as FANBOYS: for, and, nor, but, or, yet, and so. However, compound sentences can also use a semicolon to connect two clauses, in which case no conjunction is necessary.
Let’s look at some compound sentence examples to see how they work.
Compound sentence examples
Below are two simple complete sentences, each with its own subject and verb:
I have a pet iguana. His name is Fluffy.
To combine them into a compound sentence, we simply add a comma plus the coordinating conjunction and:
I have a pet iguana, and his name is Fluffy.
Alternatively, we can make a compound sentence by adding only a semicolon, and the sentence will still be correct:
I have a pet iguana; his name is Fluffy.
Although they’re talking about the same topic, the subject of each independent clause is different: The first clause’s subject is I, and the second one’s subject is name. That’s part of what makes them independent, and a sentence is considered compound only when it consists of independent clauses. For example, the sentence below is not a compound sentence:
I have a pet iguana whose name is Fluffy.
To be a compound sentence, it needs at least two subjects and two verbs. If both independent clauses use the same subject, it must be stated twice, as in the quote below, for the sentence to be compound:
“I alone cannot change the world, but I can cast a stone across the water to create many ripples.” —Mother Teresa
Be careful of sentences with only two subjects or only two verbs—these are not the same as compound sentences. The following sentence is not a compound sentence, because there is only one subject (I) even though there are two verbs (chew and study), and because what comes after the conjunction and is not an independent clause:
I came here to chew bubblegum and study grammar.
However, you can turn this sentence into a compound sentence by adding another independent clause with a second subject:
I came here to chew bubble gum and study grammar, but I’m all out of gum.
Keep in mind that imperative sentences don’t always show their subjects, because they’re implied. That leads to compound sentences like this example, the first independent clause of which has the implied subject you:
Get me some water, or the fire will spread!
Let’s look at some more compound sentence examples from some of history’s greatest writers:
“Nature does not hurry, yet everything is accomplished.” —Lao Tzu
“Be yourself; everyone else is already taken.” —Oscar Wilde
“You will face many defeats in life, but never let yourself be defeated.” —Maya Angelou
Commas and other punctuation in compound sentences
When creating compound sentences, there are two punctuation rules to keep in mind:
1 Place a comma before the coordinating conjunction.
2 If you’re not using a coordinating conjunction, place a semicolon between the clauses.
As always, you use a lowercase letter to start the second independent clause. Since compound sentences are a single sentence, only the first letter of the first clause is capitalized.
Mastering these punctuation rules is crucial for creating compound sentences. Without them, your sentence becomes a dreaded run-on sentence. In writing, run-on sentences are not only grammatically incorrect but also difficult for your reader to understand.
To avoid both run-on sentences and confusingly long compound sentences, try to limit the number of clauses in a sentence to two or three. In situations when you need more than three clauses, keep them as short as possible by removing unnecessary words. Remember, short sentences are easier to understand and give your writing a faster pace.
Compound vs. complex sentences
It’s easy to get compound sentences confused with complex sentences; both use two or more clauses in a single sentence. The most significant difference, however, is the type of clauses they use.
Compound sentences use two or more independent clauses.
I am working now, but we will eat later.
Complex sentences combine independent clauses with subordinate clauses, also known as dependent clauses.
Because I am working now, we will eat later.
In this example, because I am working now is the subordinate clause, and we will eat later is the independent clause. The clue is the word because, which is a subordinating conjunction. Words like because, if, whenever, and since—as well as certain prepositions like after and before—all act as subordinating conjunctions. Their job is to connect subordinate clauses to independent clauses.
Just by adding a subordinating conjunction, you can turn an independent clause into a subordinating clause. I am working now alone is an independent clause, but with because in front, it becomes a subordinating clause.
Be careful, though, because a sentence can be both complex and compound at the same time! A complex-compound sentence occurs when a single sentence has at least two independent clauses and at least one subordinate clause.
After I got home from work, my friends invited me out, and I left my apartment again.
In this example, after I got home from work is the subordinate clause (you can tell because the word after appears at the front). Both my friends invited me out and I left my apartment again are independent clauses, joined by the coordinating conjunction and. Put all three clauses together with the proper punctuation and you have a perfectly correct complex-compound sentence.
Polish your writing
The rules about different clauses and how to combine them can get complicated, even for lifelong English speakers. It takes some practice to get used to, especially learning all the different coordinating and subordinating conjunctions.
If you feel unsure about your English, you can always use a writing assistant like Grammarly. Our writing suggestions point out any grammar mistakes you might have missed, including run-on sentences and missing commas before conjunctions. This feedback ensures your writing is clear to your readers.
Try Grammarly now and write with confidence!