Updated: Jun 17, 2020
Perhaps it’s just me, but I find the colon the most mysterious of all punctuation. While we often have a general “sense” of how and where to use commas and semicolons, the colon seems to be less straightforward. They aren’t used as often in modern writing as the comma or semicolon and are most often found in citations. Regardless, colons are useful punctuation marks to draw attention to the words or phrase that follow them. Here are the general rules for using colons (and, as always, refer to your style guide for how colons are used in citations and quotations).
Between two independent clauses
Colons are used between independent clauses when you are using the second clause to clarify or explain what you mean in the first clause. The first letter following the colon can be capitalized or lower case, but always check your style guide if you are writing professionally. Example 1: She was a true inspiration: her activism led to major changes to the city budget and structure. Example 2: Remember the Golden Rule: Do unto others as you would have them do unto you.
Colons are used to introduce an item or list of items after an independent clause. They should not be used after a verb or verb phrase, where you would not use punctuation at all.
Colons can help the reader determine where a list starts and can indicate that the list is the focus of the sentence. When you are including the list as part of the sentence, you only capitalize the first letter if the item is a proper noun. Example: Taylor packed everything they needed into their backpack: a first aid kit, water, a phone charger, and plenty of snacks.
You should use a colon when you are introducing a list that has each item on its own line and are separated by numbers, letters, or bullet points. These items can be capitalized and punctuated as full sentences, but they don’t have to (unless your style guide gives specific rules either way). Example 1: Select the correct spelling: a. mischievous b. mischeavous c. mischevious d. misschevous Example 2: These are the pool rules: 1. Do not run on the pool deck. 2. Report unsafe behavior to the lifeguard. 3. All children under 12 years old must be accompanied by an adult. 4. The pool closes to the public at sunset.
Colons can be used to highlight quotations. The first letter of the quote should always be capitalized. Here are a few ways that quotations are used.
Quotations that are included in a sentence and introduced with a colon. Example: Marcus Aurelius, the Roman emperor and philosopher, offered powerful advice: “Do every act of your life as if it were your last.”
When you are writing dialogue in a screenplay, the name of the speaker is followed by a colon. Example: Darren: How dare you come here?
Longer quotes that are offset from the main sentence, as you see in many academic styles, are introduced with a colon. In this example, the quote starts in the middle of the sentence, so the first letter is capitalized, but offset with brackets to show that I changed the original text.
Example: Addonizio & Laux (1997) describe images in poetry as:
…[L]anguage that calls up a physical sensation, appealing to us at the level of any of our five senses. Images may be literal: the red kitchen chair in a dim corner of the room; the gritty wet sand under her bare feet. Or they may be figurative, departing from the actual and stating or implying a comparison: the chair, red and shiny as fingernail polish; the armies of sand grains advancing across the wood floor of the beach house (86).
Appositives are phrases that are used to describe a noun. They are most often indicated without punctuation or with a comma, but you can introduce them with a colon if you want to highlight the appositive. Example: Her actions were inexcusable: she betrayed my trust and ruined my friend’s career. (Consider how the weight of the sentence changes without the use of a colon: Her inexcusable actions betrayed my trust and ruined my friend’s career.)
Addonizio, Kim & Dorianne Laux (1997) The Poet's Companion: A Guide to the Pleasures of Writing Poetry. New York: Norton. Pp. 86.
Hacker, Diana. 2007. A Writer’s Reference, 6 ed. Boston, MA: Bedford/St Martins. Pp. 273-276.