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Comma

Commas are used to separate two or more grammatical elements such as

Independent clauses

Use commas to separate independent clauses that are joined by coordinating conjunctions.

  • Maria works at a hospital on weekdays, and she volunteers at a shelter on weekends.
  • Jim planned on going camping, but he went on a Caribbean cruise instead.
  • Jack will marry Jill, or he will marry Pete.
  • I don’t eat meat, nor do I associate with people who eat meat.
  • Sarah won’t be at school today, for she overslept this morning and missed the bus.
  • We have always wanted to see the desert, so we decided to drive out west.
  • I’ve never been to the mountain top, yet I am sure I know how to get there.

Do not use commas before conjunctions that link phrases.

  • Donald teaches history, and delivers pizzas for fun. (incorrect)
  • Donald teaches history and delivers pizzas for fun. (correct)

Introductions

Use commas to separate elements that introduce and modify sentences.

  • Because you didn’t finish your homework, you cannot go out and play.
  • After I walk my dog, I will come over to your house.

Dates

Use commas with dates that include a month, day, and year. There should be no space to the left of the comma and one space to the right of the comma. No comma is needed when the date consists of only the month and year.

  • On January 1, 2019, my wife gave birth to a healthy baby girl.
  • On Friday, March 14, 2000, the old post office closed for good.
  • World War II came to an end in September 1945.

Addresses

Use commas with addresses and the names of places. Notice no comma separating the state name and zip code below. If city and state occur at the beginning or middle of the sentence, place a comma after the state name as in second example. When writing city and country names, a comma follows the country name.

  • The White House is at 1600 Pennsylvania Ave NW, Washington, D.C. 20500
  • My best friend moved to Orlando, Florida, last year.
  • We will be visiting Barcelona, Spain, next summer.

Numbers

Use commas with large numbers. When inserting commas in numbers, no space should be placed on either side of the comma.

  • The new skating rink cost $1,565,000 to construct.
  • Our company harvested over 9,500 hemp plants last season.

Quotations

Use commas with quotations to separate the quoted words from the sources.

  • Astronaut Neil Armstrong was quoted as saying, “That’s one small step for man, one giant leap for mankind.”
  • “I became insane, with long intervals of horrible sanity,” wrote Edgar Allan Poe.
  • “If you’re going through hell,” said Winston Churchill, “keep going.”
  • “I do not know how the third World War will be fought,” remarked Einstein, “but I can tell you what they will use in the Fourth—rocks!”

Parenthetical material

Use commas to separate parenthetical words and phrases from the rest of the sentence.

  • My first grade teacher, an abusive and sadistic woman, taught me many lessons.
  • Religion, in my estimation, is the greatest fraud ever perpetrated on humanity.

Nouns of direct address

Always separate nouns of direct address from the rest of the sentence with a comma no matter where they occur in the sentence.

  • Rikki, don’t lose that number!
  • I don’t know, Grandma, whether you should be driving at 96.
  • I’m so proud of you, Elizabeth.

Interjections

Use commas following interjections.

  • Well, I guess it’s time to go.
  • Oh, so it’s like that?
  • Yikes, I think I just stepped on something!

Coordinate adjectives

Use commas with coordinate adjectives that modify nouns separately. Coordinate adjectives can be joined with the word “and,” and their order of occurrence can change without changing the meaning of the sentence.

  • We decided to adopt the quieter, smaller, older cat.
  • We decided to adopt the older, smaller, quieter cat.
  • We decided to adopt the quieter and smaller and older cat.

Do not use commas with cumulative adjectives. Cumulative adjectives cannot be rearranged, because they are different types of adjectives, and their rearrangement would break the general order of adjective progression.

  • The fisherman caught two small fish. (Not the fisherman caught small two fish.)
  • They discovered the entrance to a hidden ancient Egyptian royal burial tomb. (Not they discovered the entrance to a burial royal Egyptian ancient hidden tomb.)

Nonrestrictive elements

Use commas before and after nonrestrictive elements. Nonrestrictive elements can be omitted without affecting the meaning of the sentence.

  • Adam’s new truck, a Ford F-150, has tinted windows and a steel spare tire.
  • Bothered by the loud noise outside, Marcelo decided to close his windows before he went to bed.

Do not use commas to set off restrictive elements. Restrictive elements are essential to the meaning of the sentence.

  • The cute dog with no tail is up for adoption. (With no tail is needed to show which dog is up for adoption.)
  • Those students who have finished taking the test may get up and leave now. (Who have finished taking the test is necessary to understand who may get up and leave.

Parallel structures

Use commas with parallel words, phrases, and lists or series.

  • The restaurant offered an entree, a side, and a drink for five dollars.
  • The cat chased the tiny mouse down the hallway, up the stairs, and under the bed.
  • Barbara promised her kids a treat if they would finish their homework, straighten their bedrooms, and put their toys away quietly.

Prevent misreading

Use commas to prevent misreading.

  • To Steven, Tyler’s choice of music was unacceptable. (The comma clarifies that there are two people: Steven and Tyler.)

Indicate an omission

Use a comma to indicate an ommission.

  • Soon after we left, Barry closed the club. (The comma indicates the omission of the club.)
  • Herman bought a new pair of boots; Morticia, an evening gown; and Eddie, a set of fangs. (Commas indicate the omission of the verb bought.)