What Is a Comma?

A comma is a punctuation mark that separates elements within a sentence. The most common mistakes are omitting needed commas or inserting needless ones.

Use Commas:

  1. To separate parts of an address.
    Ex: Margaret lives at 423 Long View, Jordan, Minnesota.
  2. To separate numbers in a date.
    Ex: Jamie's birthday is December 20, 1970.
    December 20, 1970, is Jamie's birthday.
  3. To set off the name of the person spoken to.
    Ex: "Julie, have you finished?" he asked.
  4. To set off positive and negative replies.
    Ex: "Yes, he did finish."
  5. To separate questions from statements.
    Ex: It is tedious, isn't it?
  6. After long introductory phrases.
    Ex: In the back of the little shed on my grandfather's farm, . . . .
  7. Before coordinating conjunctions (for, and, nor, but, or, yet, and so = FANBOYS) that join independent clauses.
    Ex: He saw the rat, but she did not.
  8. To set off parenthetical expressions, particularly transitional expressions (however, on the other hand, first, in fact, and for example).
    Ex: It is, however, the right thing to do.
  9. To set off contrasting expressions.
    Ex: The dancers, not the instructors, let us down.
  10. To separate items in a series.
    Ex: I need to pick up milk, eggs, and butter at the grocery store.
  11. To set off nonrestrictive modifiers (i.e., modifiers that are not needed to identify the meaning of a term in the sentence).
    Ex: Annabel Heritage, my niece, is fifteen years old. (The fact that she is my niece is not necessary to identify Annabel.)
  12. To set off dependent elements at the end of a sentence when they are not essential to the meaning of the sentence.
    Ex: Houston won the game, although not by much.
  13. To separate coordinating adjectives (two or more adjectives, each of which modifies the noun).
    Ex: The quiet, reluctant crowd of students waited for their professor's entrance.
  14. To set off dependent clauses functioning as adverbs from the rest of the sentence.
    Ex: If the pitcher had prepared for the game, he would have struck out more batters.


Do Not Use Commas To:

  1. Set off restrictive modifiers (modifiers that are essential because they identify the meaning of a term in the sentence).

    Ex of incorrect use: My son, Jonathon, is ten.

    Ex of correct use: My son Jonathon is ten.
    (I have two sons; therefore, his name is restrictive and necessary to identify which son, so I should not include commas.)

  2. Separate compound (1) subjects, (2) verbs, (3) complements, (4) direct objects, or (5) objects of the preposition.
    Exs of incorrect usage:                                   Exs of correct usage:
    (1) Bob, and Jack went to the movies.        (1) Bob and Jack went to the movies.
    (2) Lupe took the candy, and ate it.            (2) Lupe took the candy and ate it.
    (3) The apples were firm, and ripe.             (3) The apples were firm and ripe.
    (4) James saw Carla, and Tom.                    (4) James saw Carla and Tom.
    (5) Give it to Juan, and me.                           (5) Give it to Juan and me.


  3. Separate (1) subjects from verbs, (2) complements from verbs, or (3) objects from verbs.
    Exs of incorrect usage:                                   Exs of correct usage:
    (1) I, want you to go.                                        (1) I want you to go.
    (2) I am, sick. He is, my brother.                   (2) I am sick. He is my brother.
    (3) I want, a cake for my birthday.               (3) I want cake for my birthday.

A comma is a punctuation mark that separates elements in a sentence. It is important to remember when to use them and when not to, so that you don't confuse the reader.

Page last updated June 26, 2023.