Colon Grammar Rules: How to Use a Colon Correctly

A colon (:) is a punctuation mark that initiates a list, introduces a quote, or tees up the start of an explanation. A colon is represented by two dots vertically stacked on top of each other with a bit of negative space between them.

Colons are useful in various instances in the English language, including when:

1. 1. Separating two independent clauses: You can use a colon to separate two independent clauses when the second clause clarifies or explains the first, as in “You can take me to the train station now: I am ready to leave.” Each of these independent clauses can function on its own, but with the use of a colon, the second clause clarifies the first. Capitalize the first letter of the first word of an independent clause that follows a colon.
2. 2. Starting a list of separate items: Use colons to introduce a list of items or ideas that come at the end of a sentence, as in the example “We need two ingredients from the grocery store: flour and baking soda.” In that example, “We need two ingredients from the grocery store” is a complete sentence; the colon introduces the necessary items. Lists not following a complete sentence do not need a colon, as in the example sentence “Go to the store and get flour and baking soda.” No colon is necessary after “get” because it is a transitive verb requiring direct objects, in this case “flour and baking soda.”
3. 3. Introducing a bulleted list: A colon might separate a concept from its examples. For example, you may write "There are many kinds of dogs:" and then proceed to share bullet points or a numbered list that features example breeds.
4. 4. Greeting someone in a letter or email: At the start of your business letter or correspondence, begin with "Dear sir:", "To whom it may concern:", or another greeting. In these salutations, a comma or a colon are both acceptable.
5. 5. Introducing a quote: Colons are used when teeing up a quoted source, as in the sentence "As Shakespeare wrote in Hamlet: ‘To be or not to be, that is the question.’”
6. 6. Writing dialogue: You can use a colon before quotation marks when writing dialogue (although a comma is more common). For example, "He said: 'Let's cook shrimp tonight.'"
7. 7. Titling works of art: Colons can appear in titles of art, as in Edwin A. Abbott’s novella Flatland: A Romance of Many Dimensions. Here, the first part of a title operates as the main title, and what follows the colon functions almost as a subtitle.
8. 8. Writing out times of day: Times of the day will have a colon between the hour and minute, as in the sentence, "We'll leave work at 3:30 p.m. to beat rush hour traffic."
9. 9. Creating a ratio: You can use a colon to create a numeral ratio. For example, three to one can be written as 3:1.

A colon can sometimes function similarly as an em dash or parentheses, as in the sentence “We’re going to two countries—Spain and Portugal” or “We’re going to two countries (Spain and Portugal).” A colon could also follow the word “countries” in that sentence.

Study these three example sentences to learn proper colon usage:

1. 1. He writes in three settings: in bed, at his desk, and in the writing center. A colon is used in this first sentence because the independent clause sets up the reader to expect a list, which follows the colon and shares the three locations.
2. 2. The odds of his horse winning are 17:1. This sentence shows a numeral ratio, seventeen to one, written out with a colon as 17:1.
3. 3. Susan called down: “We’re going in five minutes.” Colons can be used to introduce a line of dialogue, and the first word within the quotation marks will start with a capital letter, as in this example sentence.

Although there are rare cases where either can be used, colons and semicolons differ significantly.

• Colons help introduce new information. The primary use of the colon is to introduce new information such as a quote, list, or example. Colons signal that something is coming, while semicolons connect related ideas.
• Semicolons connect two complete sentences. Semicolons can connect two related, independent clauses. Colons typically connect dependent clauses (incomplete sentences), though there are rare cases where a colon can join two independent clauses for the purpose of emphasizing the second clause.
• Colons have many practical applications. You may use a colon to set off a book’s subtitle (Outliers: The Story of Success), express a numerical ratio (1:1), and communicate a time (4:30 p.m.). Semicolons do not have these practical uses.
• Semicolons help organize complex lists. As explained above, semicolons can provide clarity when individual items in a list use commas or other punctuation. Colons can only set off a simple list of items. For example, “I need to get these ingredients from the store: apples, eggs, milk, and butter.”

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