Grammar: English punctuation: commas

Read the rules:

Rule 1. Use commas to separate words and word groups in a simple series of three or more items. Example: My estate goes to my husband, son, daughter-in-law, and nephew.

Rule 2. Use a comma to separate two adjectives when the order of the adjectives is interchangeable. Examples: He is a strong, healthy man. We could also say healthy, strong man. Examples: We stayed at an expensive summer resort. We would not say summer expensive resort, so no comma.

Rule 3. In sentences where two independent clauses are joined by connectors such as and, or, but, etc., put a comma at the end of the first clause. Examples: Incorrect: John is making dinner in the kitchen and I'm serving the table in the living room. Correct: John is making dinner in the kitchen, and I'm serving the table in the living room.

Rule 4. When starting a sentence with a dependent clause, use a comma after it. Example: If you are not sure about this, let me know now. Follow the same policy with introductory phrases. Example: Having finally arrived in town, we went shopping. A similar meaning may be expressed without a comma. Connective words and prepositional phrases are used instead. We didn't enjoy the day because the weather was so awful. I hope to visit the British Museum while I am in London.

Rule 5. Use commas to set off nonessential words, clauses, and phrases. Examples: Incorrect: Jill who is my sister shut the door. Correct: Jill, who is my sister, shut the door.

Rule 6. Use a comma after certain words that introduce a sentence, such as well, yes, why, hello, hey, etc. Examples: Why, I can't believe this!

Rule 7. Use commas to set off expressions that interrupt the sentence flow (nevertheless, after all, by the way, on the other hand, however, etc.). Example: I am, by the way, very nervous about this.

Rule 8. Use commas to set off the name, nickname, term of endearment, or title of a person directly addressed. Examples: Will you, Aisha, do that assignment for me? Yes, old friend, I will.

Rule 9. Use a comma to separate the day of the month from the year, and—what most people forget! - always put one after the year, also. Example: It was in the Sun's June 5, 2003, edition.

Rule 10. Use commas to introduce or interrupt direct quotations. Examples: He said, "I don't care." "Why," I asked, "don't you care?"

Rule 11. Use a comma to separate a statement from a question. Example: I can go, can't I?

Rule 12. Use a comma to separate contrasting parts of a sentence. Example: That is my money, not yours.

Rule 13. Always add a comma if it would avoid confusion. Example: Last Sunday, evening classes were canceled. (The comma prevents a misreading.)

Rule 14. Use a comma to separate a city from its state, and remember to put one after the state, also. Example: I'm from the Akron, Ohio, area.

Rule 15. Use a comma before and after certain introductory words or terms, such as namely, that is, i.e., e.g., and for instance, when they are followed by a series of items. Example: You may be required to bring many items, e.g., sleeping bags, pans, and warm clothing.