A comma is used to

  • group words that belong together
  • separate words that do not belong not belong together
  • assist readers in making sense of sentences
  • follow specific established conventions.

Use commas

  • to set off introductory phrases and clauses:

    After the rain, the grass grew taller.

    To see the microbe, we took turns looking into the microscope.

  • to set off parenthetical elements that provide transitions, express afterthoughts, or offer supplemental information:

    The best Tim Burton movie is, in my opinion, Pee-Wee's Big Adventure.

  • before coordinating conjunctions (and, but, or, nor, for, yet, so) linking two independent clauses

    My sister wants a car for graduation, and my parents intend to buy her one.

    BUT NOT: My sister wants a car for graduation, and a trip to Europe.  Note: and does not link two independent clauses.

  • to separate items in a series (three or more things):

Let's order a pizza with pepperoni, green peppers, and mushrooms.

Let's drive to Sioux Falls, eat at Granite City, and watch a movie on Saturday night.

  • to follow established conventions for punctuating dates, addresses, and place names:

    • dates:  set off the year from the month and day and the rest of the sentence
      • December 8, 1941, Pearl Harbor was bombed.
    • Note: If the day precedes the month, no comma is needed: 8 December 1941 will be remembered for many decades.
    • addresses: Separate each item except the zip code in an address when the address is run together in text
      • DSU's address is 810 N Washington Avenue, Madison, SD 57042.
    • place names: separate each item in a place name
      • I go to school at Dakota State University, Madison, South Dakota, my mother's alma mater.
  • set off mild interjections, direct address, and yes and no
    • Oh, why do you think so?
    • Yes, I agree.
    • Wouldn't you agree, Tom?
  • to set off expressions such as he said and she wrote from direct quotations
    • "Go with me," she said.
      Note: omit the comma if the expression ends with a period, exclamation mark, or exclamation point.
    • "Will you go with me?" she asked.
  • to set off nonrestrictive elements in a sentence

Nonrestrictive elements provide information that is not essential to the meaning of the sentence:

Tom Cruise, a well-paid actor, lives in a luxurious mansion in Hollywood.

Note: restrictive elements, which are crucial to the meaning of the sentence, are not set off by commas:

Actors who are well-paid tend to live in luxurious mansions in Hollywood. (The predicate does not apply to all actors, but only those who are well paid.)

Note: The relative pronoun "that" always indicates a a restrictive clause and so should NOT be preceded by a comma.

Actors that are well-paid tend to live in luxurious mansions in Hollywood.

DO NOT use commas, unless sentence elements intrude that require commas, in the following cases:

  • between a subject and verb
  • between a verb and its object
  • between a preposition and its object
  • between compound words or phrases joined by a coordinating conjunction (and)
  • after "such as" and "like"


Gain extra practice using the StudyMate activities below.

Set 1 

Set 2

Last Updated: 8/29/13