Colons

Definition

A colon ( : ) is used after an independent clause to add information that helps illustrate or clarify what it says. It is most commonly used to introduce a list, but it can also introduce words, phrases, or entire clauses that complete the meaning of the clause that came before it.
First, we’ll look at when it is appropriate to use a colon, and then we’ll look more closely at all the specific ways it can be used.

When to use a colon

When using colons, the general rule is to only place them after an independent clause—that is, a clause that can stand on its own as a complete sentence and is not grammatically dependent in any way on the information that the colon introduces. Don’t use a colon after a single word or a sentence fragment, in which case a comma or no punctuation at all would be more appropriate. If you feel a colon is necessary or helpful, try to reword the introductory clause so that it could stand on its own as a complete sentence.
Additionally, because colons act as an introductory element, they stand in place of words that would perform the same task: we should not use colons after words or phrases like for example, e.g., or namely* because they serve the same purpose, and the sentence would seem redundant if a colon were used as well. We must either use a colon on its own, or an introductory adverb with a comma (or no punctuation at all) instead of a colon:
Note that you can also use dashes before words like for example and namely if you want to put emphasis on the text that follows, or you can simply use a dash on its own (but you would not use dashes and colons together). For example:
(See the section on Dashes to learn more about their uses.)
*Author’s Note
You may notice throughout this guide the tendency to introduce example sentences or lists with “For example:” or “For instance:” When introducing a list of items arranged vertically (even just a single item), it is acceptable to use single words, phrases, or sentence fragments before a colon. (Although not all style guides agree on this point.)
Furthermore, highly stylized bodies of text often require formatting that is not always in line with the grammatical conventions of day-to-day writing. The use of colons with for example creates a clearer separation in the text that makes it easier for the reader to navigate.
In less stylized writing, though, where for example or similar phrases would be embedded within a complete sentence, it would not be considered grammatically correct to use a colon to introduce the information that follows. Likewise, a colon should not be used with a word or phrase unless it can stand on its own as a complete sentence, except in the case of vertical lists.

Introducing lists

The most commonly cited use for a colon is to introduce a list of information. In many cases, the list is simply an extension of the existing sentence. This is known as a run-in list or horizontal list. For example:
  • “In my opinion, the perfect sandwich has only three things: ham, cheese, and mayonnaise.”
  • “There are three new members of the faculty whom I would like to introduce: Janet Baker, Professor of Literature; Tom North, Professor of Economics; and Susanne Whitefield, Professor of Philosophy.”
  • “There are two things that I love doing more than anything: reading and water skiing.”
When we write a list in this way, there is no particular importance given to one item over another; it might be implied by the order of the sentence, but it is not explicit. If we want to indicate the importance of the items in a list, we have to number or letter it.

Numbered lists

If a strict order needs to be established, we can use numbered lists to specify which items should be accomplished or attended to first. Consider the following examples:
  • “Your assignment for the evening is as follows: (1) interview an older relative about his or her experiences growing up; (2) write down your own experiences for the same time period; (3) write a one-page report that compares and contrasts your experiences to those of your relative.”
  • “The schedule for the seminar will be structured in the following way: (1) welcoming of attendees; (2) introduction of keynote speakers; (3) presentations from first and second speakers; (4) one-hour lunch break; (5) presentations from third and fourth speakers; (6) closing remarks.”
Notice that we put the number or the letter in parentheses, and we mark the end of each item with a semicolon. We also do not use a coordinating conjunction before the last item in a list like this.

Lettered lists

When we want to highlight each item in a list—especially if the list presents a selection that someone must make or if the item will be referred to again later—we can also use lettered lists. We format lettered lists in the exact same way as numbered lists, except that we substitute sequential lowercase letters for the numbers. For example:
  • “We’ll need four things for the upcoming audit: (a) copies of all bank statements over the last year; (b) a letter from the bank confirming your company’s signatories; (c) any receipts for business-related purchases made this year; (d) a profit and loss report for the year to date.”

Vertical lists

While using numbers or letters can help to better organize a list, it can also result in rather long, clunky sentences, as we saw above. In many cases where numbers or letters are necessary, writers often prefer to structure their lists vertically—that is, with the contents of the list appearing in individual lines indented beneath the introductory clause. We can also create vertical lists that use bullet points or no marks at all. Let’s look at some examples.
“Your assignment for the evening is as follows:
  • 1) Interview an older relative about his or her experiences growing up.
  • 2) Write down your own experiences for the same time period.
  • 3) Write a one-page report that compares and contrasts your experiences to those of your relative.”
“We’ll need four things for the upcoming audit:
  • a) Copies of all bank statements over the last year
  • b) A letter from the bank confirming the company’s signatories
  • c) Any receipts for business-related purchases made this year
  • d) A profit and loss report for the year to date”
“There are a few tasks we need to address at the next meeting:
  • reaching a wider consumer demographic;
  • developing a stronger presence on social media; and
  • deciding on the slogan for our new advertising campaign.”
“Below are the most common punctuation marks used in English:
  • Periods
  • Commas
  • Question marks
  • Exclamation points”
Note that there is a wide variety of opinion regarding when and how (and even if) to punctuate and/or capitalize elements in a list. For the most part, this comes down to stylistic preferences rather concrete “rules” about the structure, so check with the style guide of your school or employer.

Introducing other text

While we most commonly use colons to introduce lists, there are also instances in which they can be used to introduce words, phrases, clauses, or even multiple sentences that help explain or illustrate the previous clause. For example:
  • “One thing is for sure: we aren’t going to get a better deal than the one they’re offering today.”
  • “Let’s get something straight: We are not at an equal level. I’m the boss, and you are an employee of this company, so what I say is final.”
  • “Many people will try to sell you ‘easy’ ways to become successful, but it really comes down to just one thing: hard work.”
Again, we must be sure to use only independent clauses before colons when we do this. If the clause can’t stand on its own, we must either rewrite the sentence or omit the colon altogether:
Capitalizing after a colon
Notice in our examples above that the sentences following the colons are sometimes capitalized, sometimes not. There is a bit of debate regarding when (and if) to capitalize the first word of a complete sentence when it follows a colon, but in reality this largely comes down to the stylistic preferences of the writer, as there are many different competing “rules” among style guides.
A good standard to apply to your writing is this: If a colon is introducing a short, complete sentence that flows naturally with the previous clause, there is no need to capitalize the first word. If the sentence after the colon is particularly lengthy (and the clause before the colon is very brief), or the information introduced by the colon spans across multiple sentences, then capitalize the first word.
This is ultimately just a suggestion, however. There is no concrete rule for capitalizing sentences after a colon, so it comes down to the preference of the writer. You should also be mindful if your school or organization follows a particular style guide; if so, then be sure to follow the rules that it prescribes.

Quotations

Another common reason to use a colon is to introduce a complete quotation, especially if a reporting verb (such as said, told, asked etc.) is not used. For example:
  • Always remember Polonius’s famous line in Hamlet: “This above all else: to thine own self be true.”
  • My father had a phrase he was fond of repeating: “Hope for the best, but prepare for the worst.”
Remember that we only use a colon after an independent introductory clause; if the text before the quotation is a fragment, then we must either use a comma (if a reporting verb is used) or no punctuation at all, or else rewrite the sentence. For instance:
Note that while it is optional to capitalize the first letter after a colon when introducing non-quoted sentences, we should always capitalize the first letter when we introduce a quoted sentence.

Other technical uses

In addition to its grammatical function of introducing lists or illustrative information, the colon is also used for a number of technical, non-grammatical reasons in writing.

Writing the time

One of the most common technical uses for a colon is when writing the time numerically. The colon is placed between the numbers representing the hour and the minutes of that hour (without any spaces), as in:
  • “Our flight is at 8:30, so we’ll need to be at the airport by 6:30 AM at the latest.”
Very occasionally, we write the seconds as well as the hour and minutes:
  • “Mr. President, at 22:37:45, unauthorized foreign aircraft entered US airspace.” (Notice that the hour is in military time, meaning 10 PM.)
Another situation in which we might write time numerically is when indicating how much time is remaining for something to occur, such as for a timer or countdown. For example:
  • “The space shuttle is scheduled to launch in 01:32:45.” (one hour, 32 minutes, and 45 seconds)

Writing numerical ratios

Colons are also used with numeric writing when we want to express a ratio between two amounts. For example:
  • “The proportion of international students compared to US-born students in the university has increased to nearly 2:1.” (There are almost twice as many international students as there are US students.)

Citing Bible chapters & verses

One specific use of the colon is to indicate the specific verses that appear in a chapter of the Bible. Similar to how we write numerical times and ratios, we place the colon between the number of the chapter and the number of the verse(s), with no spaces in between. For example:
  • “One of my favorite passages is from 1 Corinthians 13:4–7, which begins, ‘Love is patient, love is kind.’” (The passage is from the fourth through seventh verses in chapter 13 of 1 Corinthians.)

Citing pages from a journal volume

We also use colons to indicate a page or range of pages from a volume of an academic journal. It is formatted in the same way as when we cite a chapter and verse(s) from the Bible (except the title of the journal is in italics):
  • “According to Smith, unemployment should decrease to around 4% by the year 2020 (Journal of Economic Studies 8:25).” (The sentence is referencing information found on page 8 of volume 25 of the journal.)
(Note that there are other uses for colons when creating longer citations for academic writing. You should check the style guide used by your academic institution for the proper way to format your citation, as the specific styles vary quite a bit.)

Written correspondence

In written correspondence, especially in business, we sometimes use a colon after a formal salutation (the introduction that includes the name or title of the recipient). For example:
  • “Dear sir or madam:
  • I wish to make you aware of a recent change to your account …”
  • “Mr. and Mrs. Philips:
  • In reference to your recent application, please find enclosed …”
We also use a colon after certain introductory phrases or abbreviations:
  • “RE: Your recent application”
  • “PS: Please remember to bring your swimsuit to the party!”

Writing dialogue

One final use of the colon occurs in written dialogue between two or more people, most often in transcripts of plays or legal testimony in a courtroom.
We place the colon immediately after the name of the speaker (which is often in all capital letters), followed by the dialogue (without quotation marks). In a play, if there is any stage direction or other information about the character, it appears in parentheses immediately before the colon. For example:
  • DIANNE: You’re lying to me again! Tell me the truth!
  • ANTHONY (backing up nervously toward the door): I can explain! It’s all just a big misunderstanding.
  • PROSECUTOR: Tell the court again your whereabouts on the evening of August 12, 2010.
  • DEFENDANT: As I’ve said already, I was at home with my parents for the entire evening.
Usage Note: Spaces after a colon
Whenever we use a colon (except when writing times, ratios, or citations), it will be followed by a single space before the list or other information.
When typewriters were used, it was common practice to place two spaces after a colon to make the writing clearer. However, now that most writers use word processors, which space letters automatically to make them easier to read, this second space is unnecessary. Always use just one space after a colon.
Quiz

1. When are we able to use a colon to introduce a list or explanatory information?





2. What is the function of a numbered list?





3. Which of the following can come after a colon to help explain, clarify, or illustrate the previous clause?







4. Which of the following is the correct way to write the time numerically?





5. When must we capitalize the word immediately after a colon?





Complete English Grammar Rules is available for purchase as Paperback and Kindle eBook.
Share Tweet Share

Conversations