Colons  

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 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.)

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:

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.

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:

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.

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:

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:

“We’ll need four things for the upcoming audit:

“There are a few tasks we need to address at the next meeting:

“Below are the most common punctuation marks used in English:

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.

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:

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:

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:

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.

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.

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:

Very occasionally, we write the seconds as well as the hour and minutes:

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:

Colons are also used with numeric writing when we want to express a ratio between two amounts. For example:

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:

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):

(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.)

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:

We also use a colon after certain introductory phrases or abbreviations:

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: