Use a Comma in a Compound Sentence

Knowing when and how to use punctuation properly, particularly a comma, is often difficult. One of the more common ways a comma is used is in a compound sentence, which consists of joining two independent clauses. By recognizing where one independent clause ends and the next begins, as well as learning the words which are used to connect the two, you can easily identify where a comma should be placed.

Steps

Usage Chart

Doc:Compound Sentence Comma Usage

Using a Comma in a Compound Sentence

1. Write a complete thought using both a subject and a verb. This is called an independent clause, as it is a group of words that has both a subject and verb and forms a complete thought.
   • For example, “Mom makes me breakfast before school.” In this example, “mom” is the subject and “makes” is the verb. It also forms a complete thought or sentence.
2. Write a second complete thought that closely relates to the first. Your second independent clause should also contain both a subject and a verb, but it should relate to your first independent clause.
   • For example, “I don’t have enough time to eat it.” This independent clause closely relates to the first clause you wrote and contains both a subject, “I” and a verb, “have.”
3. Connect the two independent clauses. To form a compound sentence, you will need to connect your two independent clauses together with a coordinating conjunction. There are seven commonly used coordinating conjunctions or words.
   • Coordinating conjunctions include: and, but, yet, nor, or, for, so.
   • One of the easiest ways to remember the coordinating conjunctions is to form an acronym. The most commonly used acronym is: FANBOYS (F-for, A-and, N-nor, B-but, O-or, Y-yet, S-so).
   • For example, “Mom makes me breakfast before school, but I don’t have enough time to eat it.”
4. Insert a comma before the coordinating conjunction. A comma is used to add clarity. Therefore, it’s important to use a comma when connecting two independent clauses, as you want to ensure your readers know the two are related.
   • For example, “Mom makes me breakfast before school, but I don’t have enough time to eat it.”
   • Make the beginning of the second independent clause lowercase. Now that you have both a coordinating conjunction and a comma in place, you need to make the first letter of your second independent clause lowercase.
   • In the above example, you would need to keep the “I” capitalized as it is a proper pronoun. However, another example would be, “Mom makes me breakfast before school, but my dog always steals the food before I can eat it.”
   • In this case, the “m” in “my” was capitalized when it was an independent clause - “My dog always steals the food before I can eat it.” Now that it’s part of a compound sentence, connected by a comma and a coordinating conjunction, the “m” is lowercase.

Using a Comma in a Complex Compound Sentence

1. Write a compound sentence. Join two independent clauses, or complete thoughts, together using both a coordinating conjunction and a comma.
   • For example, “Mom makes me breakfast before school, but I don’t have enough time to eat it.”
2. Construct a dependent clause. Unlike an independent clause, a dependent clause does not form a complete thought because it begins with a subordinating word (when, if, because). However, make sure the dependent clause still relates to your compound sentence, as your goal is to connect the two, by forming a complex compound sentence.
   • For example, “Because I am always hungry in the morning.”
3. Connect a compound sentence and dependent clause with a comma. When the dependent clause comes before the compound sentence, you can use a comma to connect the two, to form a complex compound sentence.
   • For example, “Because I am always hungry in the morning, mom makes me breakfast before school, but I don’t have enough time to eat it.”
   • Notice the “m” in “mom” becomes lowercase, once you’ve connected the dependent clause with a comma.

Avoiding Common Mistakes

1. Use a comma before the coordinating conjunction. When forming a compound sentence, make sure the comma is always placed before the coordinating conjunction and not after it.
   • For example, “Mom makes me breakfast before school, but I…”
2. Avoid a comma splice. A comma splice occurs when you use a comma with two independent clauses, without using a coordinating conjunction.
   • For example, “Mom makes me breakfast before school, I don’t have enough time to eat it.” This is incorrect, as a coordinating conjunction wasn’t used. The two independent clauses should have been formed into two complete sentences using a period. “Mom makes me breakfast.” “I don’t have enough time to eat it.” Another option is to use a semicolon: "Mom makes me breakfast before school; I don't have enough time to eat it." You could also use a coordinating conjunction: "Mom makes me breakfast before school, but I don't have enough time to eat it."
3. Use a comma when the dependent clause comes first. When forming a complex compound sentence, if the dependent clause is before the compound sentence, you can use a comma. Otherwise, if the dependent clause comes after a comma isn’t needed.
   • For example, “Because I am always hungry in the morning, mom makes me breakfast before school, but I don’t have enough time to eat it.” You would not use a comma if the complex compound sentence was, “Mom makes me breakfast before school, but I don’t have enough time to eat it because I don’t wake up early enough.”

Related Articles

• Use Commas
• Use English Punctuation Correctly

Sources and Citations

See also

• Use Quotation Marks
• Use Question Marks
• Use English Punctuation Correctly
• Use a Semicolon
• Use a Colon in a Sentence
• Use Commas
• Use a Dash in an English Sentence
• Use Apostrophes

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