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Punctuation Guide: Commas, Colons, and Semicolons

Commas, semicolons, and colons - an overview

The comma, semicolon, and colon are often misused because they all can indicate pauses.

Commas show a separation of ideas in a sentence.*

  • We went shopping, and then we went out to lunch. Separation of two complete ideas. 
  • Dana wanted the black, green, and blue jelly beans. Separating lists in sentences.

Commas go after introductory phrases.

  • One day, Lori called to invite me to lunch.

Commas go after a transition word.

  • Tucker tried to catch a squirrel. However, he was always too slow. 

If two sentences are joined together without the comma and the coordinating conjunction (and, or, but, etc.) then it's a run-on sentence. For more information, visit the Run-On and Sentence Fragment page on the Grammar Guide. 


Semicolons (;) are used to connect independent clauses (works best when the clauses are closely related).

  • James' back was hurt; the bathtub weighed more than he expected.

Semicolons go before connecting words or phrases.

  • Tim's birthday is tomorrow; therefore, I must get him a card today.
  •  I've known about that quiz for a week; as a result, I feel prepared.

colon (:) has three main uses:semicolons and colons are kind of a big deal

After a word introducing a quote, explanation, example, or series.

  • He was planning to try new fruits: kiwis, mangoes, melons, and plantains.

Between independent clauses when the second explains the first, similar to a semicolon.

  • I didn't have time to get changed: I was already late.

For emphasis.

  • There was one thing she loved more than any other: her dog.
  • There was only one emotion they felt when they saw the monster: fear.

More Comma Rules

QuotationsUse a comma before a quotation when an introductory phrase is before the quote.

  • She said, "How are you today?"

Titles: If a title follows a name, separate the title from the rest of the sentence with a pair of commas. 

  • Anna Johnson, MD, is a primary care doctor.

Addresses:  Use a comma to separate each element in an address. Also, use a comma after a city-state combination within a sentence.

  • Rowan-Cabarrus Community College is located at 1531 Trinity Church Rd., Concord, NC., 28027
  • Charlotte, North Carolina, is a great city.

Numbers: In numbers more than four digits long, use commas to separate the numbers into groups of three, starting from the right. In numbers four digits long, a comma is optional. 

  • 3,500 (comma is optional)

  • 5,000,000

Dates:  In dates, the year is set off from the rest of the sentence with a pair of commas. 

  • On December 7, 1941, Japan staged a surprise attack on Pearl Harbor.

Colons

References

  • Genesis 1:1 starts "In the beginning God created the heavens and the earth."

Ratios

  • It's myth that the ratio of women to men in Nottingham is 6:1.

Times

  • My favorite time of the day is between 8:00 pm and 10:00 pm.
  • The 100 meter world record is 10:49:57. 

(Colons are used in timings greater than a minute.)

Titles

  • "Star Wars: The Last Jedi"

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