How do you use a colon?

It looks a lot like the semicolon, but the meaning and usage of the colon are different. The colon expresses a clear connection between the parts of the sentence in which it is used: the second clause gives more information about the topic of the first.

What are the rules?

For a sentence including a colon to be grammatically correct, the first part of the sentence (the part before the colon) must be an independent clause. Using any kind of fragment before a colon is improper. For example: this sentence is just the kind of thing you should not write. “For example” is being used as an introductory expression (technically a conjunctive adverbial), but because it cannot stand alone as an independent clause, it cannot be used to precede a colon.

Secondly, the information that follows a colon should continue the ideas that came before it. If you imagine substituting the word “specifically” in place of the colon, it should still loosely make sense. Consider this example:

English is a complicated language: there are exceptions to almost every rule.

English is a complicated language.
Specifically, there are exceptions to almost every rule.

This sentence works because the colon is preceded by an independent clause and the clause that follows tells why English is complicated. The second part elaborates on the idea from the first, just as it should. Now consider the following:

I like to travel: I am also a good student.

This example does not work. Even though the first part is an independent clause, the two do not have the right relationship. If you substituted “specifically” in place of the colon, what would happen?

I like to travel. Specifically, I am also a good student.

What? The ideas don’t follow, since the second has no clear relationship to the first. As a result, a colon should not be used here.

Capitalization

There is also some disagreement about whether the part of the sentence that begins after the colon should be capitalized. If what follows the colon is a complete sentence (an independent clause) as in the examples above, then it is acceptable to use a capital. So, you could write the previous sentence like this:

English is a complicated language: There are exceptions to almost every rule.

However, it is equally as acceptable to use the lower case and the choice is merely a stylistic one. Note that you should never capitalize the part following the colon if it is not an independent clause on its own.

Lists

Colons are also occasionally used to introduce lists, which is fine so long as the sentence in question follows the established rules: the part preceding a colon must be an independent clause. Even if you are going to list items vertically, you must use an independent clause before the colon. For example, consider the following:

• The previous line is an independent clause
• A colon is used, but a period could easily be substituted

Notice that “Consider the following” counts as an independent clause. Where is the subject, though? Imperative sentences like this use an implied subject “you”, which will be described more in the next article.

However, in most cases example words in the midst of a sentence like “such as” or “including” should not be followed by a colon. If you want to say, “I have been to many countries, including: America, Korea, and Japan,” then you should not use a colon. Simply removing the colon would make this sentence correct.

Formal Letters

You also use a colon after the salutation of a formal letter. When writing a business or academic communication, begin by stating the name and title of the person you are writing to.

Dear Mr. Blueberry:

This is how the opening to a formal letter should look. Likewise, if you do not know the name of the person to whom you are writing, as may be the case on a cover letter or job application, you can simply write a polite general phrase.

Dear Sir or Madam:

Either way, the phrase is followed by a colon, and the letter should begin two lines below.

Formatting Uses

Colons also play a role as part of the standard format for writing several basic forms of information, like the time. You separate the hour from the minutes using a colon, as in 7:45 p.m. Furthermore, if you are writing on math-related topics you may need to write a ratio, which also uses the colon to separate one value from another. You might talk about a one-to-one ratio, for example, which could be written 1:1.

Practice Time!

Determine whether the sentences below use colons correctly. If one is incorrect, state why: (a) not preceded by an independent clause or (b) improper relationship between statements. Check your answers at the end of the page.

1. This summer has been so hot: you could probably fry an egg on the sidewalk.
2. Please bring: your own lunch, good walking shoes, and an umbrella.
3. My best friend has a cat: my favorite type of pet is a dog, though.
4. In High School I played: football, soccer, and tennis.
5. There are plenty of examples of good English: just read a good book and you will find them!
6. My courses this semester include: biology, chemistry, and physics.
7. There are so many reasons to travel: you can learn about new cultures and widen your understanding.
8. English punctuation marks often have many uses: there are lots of different grammar rules to know too.
9. Call me: I’ll be waiting to hear from you.
10. Sentence parts, such as: subjects, verbs, and objects are important in English.

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(Answers: 1.correct 2.a 3.b 4.a 5.correct 6.a 7.correct 8.b 9.correct 10.a)

Want to see them written properly, just for reference? Check below.

1. This summer has been so hot: you could probably fry an egg on the sidewalk.
2. Please bring your own lunch, good walking shoes, and an umbrella.
3. My best friend has a cat; my favorite type of pet is a dog, though.
4. In High School I played football, soccer, and tennis.
5. There are plenty of examples of good English: just read a good book and you will find them!
6. My courses this semester include biology, chemistry, and physics.
7. There are so many reasons to travel: you can learn about new cultures and widen your understanding.
8. English punctuation marks often have many uses; there are lots of different grammar rules to know too.
9. Call me: I’ll be waiting to hear from you.
10. Sentence parts, such as subjects, verbs, and objects, are important in English.