Using Commas Correctly

The comma is the busiest punctuation mark, and using it well makes writing clear instead of confusing. The editing questions test a handful of comma rules again and again, so learning those few patterns pays off quickly.

Commas separate parts of a sentence so readers can follow the meaning. Four uses cover most cases: between items in a list, after an introductory word or phrase, around extra information, and before a coordinating conjunction that joins two complete sentences. These four patterns cover many common editing questions.

Lists, Introductions, and FANBOYS

Use commas to separate three or more items in a series: We bought apples, bread, and cheese. In the serial-comma convention used here, include the comma before “and”. Some other style conventions omit it when the meaning remains clear. Use a comma after an introductory dependent clause and after introductory elements that require separation. A comma after a short introductory prepositional phrase may be optional when the meaning is clear: After the storm, the streets flooded. Required after a dependent clause: After the storm ended, the streets flooded. The earlier short phrase “After the storm” can also take a comma for clarity, but omitting it does not automatically make the sentence wrong. Use a comma before a FANBOYS word (for, and, nor, but, or, yet, so) when it joins independent clauses. A comma may be omitted when the clauses are short and closely related, as in “I called twice but no one answered.” For longer clauses, use the comma to mark the separation: I called the main office twice before noon, but no one answered any of my questions. Do not add one when the conjunction joins only two words: I called and waited needs no comma.

Setting Off Extra Information

Use a pair of commas to surround extra information that could be removed without changing the core meaning. This is called a nonessential element. Wrong: My sister who lives in Texas is visiting. If she is your only sister, the phrase is extra and needs commas. Corrected: My sister, who lives in Texas, is visiting. Ask whether the phrase identifies which person or thing is meant. An essential phrase may be removable without breaking the grammar, but removing it changes the reference. Use commas only when the information is truly supplementary. But if the information is essential to identify what you mean, use no commas: The student who scored highest won the prize needs the phrase to tell which student. Wrong: The book, that I borrowed, is overdue. That phrase is essential, so remove the commas. Corrected: The book that I borrowed is overdue.

Watch: A Short Video Lesson

Khan Academy gives a clear overview to go with this lesson:

A Routine for Commas

1. Add commas between three or more items in a list.
2. Check introductory clauses and phrases; short clear prepositional phrases may not need a comma.
3. Add a comma before a FANBOYS word joining two full sentences.
4. Surround truly extra information with a pair of commas.

Practice

1. How many items must a list have to need commas?
2. Where does a comma go with an introductory phrase?
3. When do you put a comma before “but”?
4. Fix this: “When the morning came we left early.”
5. The speaker owns one car, and its color is extra information. Add commas: “My car which is red needs gas.”
6. Does “The dog that barks lives here” need commas?

Answers

1. Three or more.
2. After an introductory dependent clause or another introductory element that requires separation, before the main clause; a short clear prepositional phrase may not need one.
3. When it joins two complete sentences.
4. “When the morning came, we left early.”
5. “My car, which is red, needs gas.”
6. No — the phrase is essential.

Where This Fits in Your RLA Prep

Commas work alongside other punctuation marks and support fixing run-ons and comma splices. See every topic on the Language Arts Prep Hub.

Recommended Prep Books

Keep building momentum with a full study guide and practice tests: