Definition and Examples of Colons

This punctuation mark introduces clauses and series

colon - punctuation
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The colon ( : ) is a mark of punctuation used after a statement (such as an independent clause) or that introduces a quotation, an explanation, an example, or a series. In addition, the colon usually appears after the salutation of a business letter (Dear Professor Legree:), between the chapter and verse numbers in a biblical citation (Genesis 1:1), between the title and subtitle of a book or article ("Comma Sense: A FUNdamental Guide to Punctuation"), and between numbers or groups of numbers in expressions of time (3:00 a.m.) and ratios (1:5).

History

The word colon comes from the Greek term kōlon, meaning a part of a verse or clause, or more literally, part of a limb, particularly a leg. Keith Houston, who has authored several books on punctuation, explained the origin of the colon in his article "The Mysterious Origins of Punctuation" published on Sept. 2, 2015, on the BBC website. Houston said the punctuation mark originated, ultimately, during the third century B.C., in the Hellenic Egyptian city of Alexandria.

A librarian there named Aristophanes developed a series of three dots to break up the unbroken stream of text that had been the norm in writing at the time. The dots, aligned with the middle, bottom, or top of each line, represented what today would be a colon, comma, and period, respectively. Though the Romans disregarded the punctuation marks after conquering the Greeks, the dots eventually were given new life in the seventh century by Isidore of Seville.

Ashley Timms in her Dec. 28, 2016, article, "A History of Punctuation in English," published on the website of Unravel Magazine, a linguistics journal, detailed the timeline: In his work "The Etymologies" (or Etymologiae in Latin), Isidore of Seville explained that the highest dot marked the end of a sentence, the lowest dot functioned much like a comma does today, and the middle dot represented a pause somewhere in between the two:

"The work of Isidore of Seville was widely respected and he was even cited by Dante Alighieri and quoted by Geoffrey Chaucer. Etymologiae was treated as a textbook through the Middle Ages and no doubt had a profound effect on how writers used grammar and punctuation."

Eventually, the middle dot evolved into two dots possibly through Gregorian chants, which included punctus elevatas (raised dots) that looked like the modern-day colon, says Timms.

Purpose

The "Associated Press Stylebook, 2018" provides possibly the best explanation (among the various style guides) of the purpose and use of the colon. The AP says the punctuation mark should be used for:

  • Emphasis: The AP gives this example: He had only one hobby: eating.
  • Lists: The colon usually comes at the end of a sentence or phrase to introduce lists, tabulations, and texts.
  • Listings: Use the colon in such listings as time elapsed (1:31:07.2), time of day (8:31 p.m.), as well as biblical and legal citations (2 Kings 2:14; Missouri Code 3:245–260).
  • Dialogue: An example would be: Bailey: What were you doing the night of the 19th? Mason: I refuse to answer that.
  • Question-and-answer interviews: The AP gives this example: Q: Did you strike him? A: Indeed I did.

    The AP says you can use a colon to introduce a direct quotation of one sentence that remains within a paragraph. You would also use a colon to introduce long—or block—quotations. When doing so, enter a hard return on the keyboard after the introductory text to bring the quoted material to the next space down, as shown in the history section above.

    Use and Misuse

    Use the colon at the end of a sentence, after initials and abbreviations, after other punctuation marks, in computing and math, and in Bible verses, among other instances.

    At the end of a sentence: Use the colon instead of a period when the two clauses have a connection such that a period would be too hard of a break. Capitalize the first word after a colon only if the colon is followed by a proper noun or an independent clause. These examples are adapted from the Associated Press and June Casagrande's book, "The Best Punctuation Book, Period: A Comprehensive Guide for Every Writer, Editor, Student, and Businessperson":

    • Right: He promised this: The company will make good all the losses.
    • Wrong: Refrigerator temperature is critical: if it's not cold enough, food will spoil.
    • Right: Refrigerator temperature is critical: If it's not cold enough, food will spoil.

    Before a list: Capitalize the first letter of the first word after the colon only if it is a proper noun.

    • Right: Joe invited several friends to the party: Samantha, David, and Frank.
    • Right: The pizza came with three toppings: pepperoni, onion, and mushrooms.
    • Wrong: The pizza came with three toppings: Pepperoni, onion, and mushrooms.

    After quotation marks and other punctuation: Use a colon after other punctuation marks but never before:

    • The truth was simple (almost too simple): Dan was guilty.
    • The truth, she said, was "simple": Dan was guilty.

    Bible verses: Cite listing the number of chapter and verse(s) in this form:

    • Matthew 3:16
    • Luke 21:1–13
    • 1 Peter 2:1

    Math and computing: Some styles—though not the AP—use colons to separate parts of a ratio, as in:

    • 2:5, which means a 2-to-5 ratio, two out of five, or 2/5
    • 3:4, which means a 3-to-4 ratio, three out of four, or 3/4

    Additionally, you can also use a colon to separate a book title and subhead, such as for Casagrande's book listed previously in this section. Use a colon in a citation to separate the chapter and page number, as in:

    • Journal of English Language Learning 15:220–229

    Also, never combine a dash and a colon.

    Linking Equal Ideas

    Generally, use colons to show that two sentences, or a sentence and a clause, are parallel or relate to the same idea or subject, says David Crystal, author of "Making a Point: The Persnickety Story of English Punctuation." Examples would be:

    "A liberal arts education creates citizens: people who can think broadly and critically about themselves and the world."
    —William Deresiewicz, "Faulty Towers," The Nation, May 23, 2011
     

    "I was going to buy a copy of 'The Power of Positive Thinking,' and then I thought: What the hell good would that do?"
    Ronnie Shakes, standup comedian

    In the first quote, which joins a sentence followed by a nonsentence clause, Deresiewic uses the colon to show that citizens who receive a liberal arts education are the same group as people who can think broadly and critically. The second, by the late Shakes, who was a frequent guest on late-night television shows, uses the colon (and irony) to show two sides of himself: the optimist who was going to buy a book about positive thinking and the pessimist who talked himself out of it.