Knowing when, where, how many, and/or why to place commas in text can be the most persnickety task involved with precise writing, editing, and proofreading work.

There are numerous style guides that can help with comma placement; however, most of them agree on a few common-sense basics.

Rules for Comma Use

1. Use commas before coordinating conjunctions (and, but, for, not, or, so, etc.) joining independent clauses unless they can be easily understood:

• Yes: Mike jumped up and down, and put the ball through the hoop.

• No: Susan sings and Sally dances.

2. Use commas to separate words, phrases, and clauses in a sentence:

• Jim ate beans, onions, and tortillas.

• John tore down the old house, drafted new design plans, and built a new house.

• During the holiday season, thousands of people take time away from work.

3. Use commas between coordinate adjectives (adjectives that separately modify the same noun):

• Matt ate the juicy, red apple.

• Sarah walked down the long, empty hallway.

4. Use commas to set off a parenthetical comments (an “aside”) if it is brief and closely related to the rest of the sentence:

• The elves, for example, are the happiest of the toy-making lot.

• Santa Clause, to be sure, is also a very happy individual this time of year.

5. Use commas to set off non-restrictive (unessential) appositives:

• Yes: Mark Twain, the American author, was famous for his sarcasm.

• No: The American author Mark Twain was famous for his sarcasm.

6. Use commas to set off non-restrictive clauses beginning with Who, Whom, Whose, Which, and That:

• Yes: Aliens, who do not follow our laws, make their own rules.

(As in, no aliens follow our laws.)

• No: Aliens who do not follow our laws make their own rules.

(As in, not all aliens make their own rules; only those who do not follow our laws!)

7. Use commas to set off non-restrictive adverbial phrases and clauses:

• Yes: The movie takes place in the mountains, where it is often cold.

(The focus is on the mountains, not the temperature; that’s just an aside.)

• No: The movie takes place in the mountain areas where it is cold.

(The focus is specifically on the mountain areas where it is cold.)

8. Use commas after a long introductory phrase or clause:

• After many years of enduring endless hardship, Mary threw in the towel.

• Although he ate everything on his plate, he was still hungry.

9. Use commas to set off alternative or contrasting phrases:

• It is Juan, not Marco, who wanted to go swimming.

10. Use commas in a date whose order is month, day, and year:

• Mrs. Clause was born on December 25, 1805, and still lives at the North Pole.

If you still need some help with often-confounding commas, you can seek out specific help from these often-used style guides:

• The Chicago Manual of Style

• MLA Handbook for Writers of Research Papers

• Publication Manual of the American Psychological Association

• The CSE Manual for Authors, Editors, and Publishers

One last tip-if in doubt, read it out loud! You can often “hear” where a comma belongs!