Basic Rules for Commas

Basic Comma Rules

1. Use a comma to separate three or more items in a list.
Example: Today I went to school, did laundry, and listened to music.
Compare: Today I went to school and listened to music. (There’s no comma for two items.)

2. Use a comma after an introductory word, phrase, or dependent clause.
Example (Introductory word): Finally, I finished my homework.
Example (phrase): During the basketball game, he injured his knee.
Example (dependent clause): After I finish watching TV, I will do my
homework.

3. Use a comma before a coordinating conjunction.
Example: I love exercise, so I go to the gym everyday.

4. Place a comma before and after the name of the person to whom you are speaking.
Example: Did you know, John, that NTU is the best school in Taiwan?

5. Place a comma before and after an appositive (additional, secondary information).
Example: Sean, my teacher, is from California.
--Notice that the sentence could just be, “Sean is from California.” The “my teacher” description is secondary information.
Example: Jay Chou, a famous singer, directed a movie.

6. Place a comma before and after words that “interrupt” a sentence.
Example: Studying hard, however, does not guarantee that you will get a good grade.
--Notice that the sentence should be, “Studying hard does not guarantee that you will get a good grade.” “However” ‘interrupts’ the sentence.
Other interrupting words include “of course” “by the way” “on the other hand” “I believe” “I think”
Example: I live in Taipei. Taipei is, of course, the largest city in Taiwan.
Example: I am going to the movies with Nancy. Nancy, by the way, is my cousin.
Example: I like vanilla. Chocolate, on the other hand, I don’t eat very often.
Example: Today’s test, I think, was only a practice test.

Comma Splice
A comma splice is a mistake. A comma splice happens when a sentence tries to link two independent clauses with a comma but without a coordinating conjunction.
Example: I went to the movie, it was entertaining.
This is a comma splice. You should not write this sentence.
A correct sentence: I went to the movie, and it was entertaining.