What Are Colons?

Colon or Semicolon

The colon is an oft-misused punctuation mark and part of that misuse comes from its resemblance to the semicolon. Though they look similar and share a key on your computer keyboard, there is a big difference between a colon, which is two vertical periods (:) and a semicolon, which is a period on top of a comma (;).

The main reason to use a semicolon for is to identify what is known as an independent clause, which is a group of words in a sentence that can stand alone as a sentence. Semicolons can replace a period but should only be used between two closely related sentences or independent clauses. Try to identify the independent clause in this sentence.

John worried about failing math, which was his worst subject.

The independent clause is ''John worried about failing math'' because if you stopped there and put a period, it would be a complete sentence (subject + verb + complete thought = complete sentence). The second half of the sentence, however, cannot stand by itself, making it a dependent clause. So, now let's use some colons.

With Independent Clauses

Probably the most common use of a colon is coming between an independent clause and dependent clause or phrase (cannot stand alone as a sentence). It is often used to introduce lists:

I went to the store and bought groceries: eggs, milk, bread, and cheese.

The colon comes at the end of the independent clause to introduce the list. However, remember that the stuff before the colon needs to be an independent clause. You will sometimes see lists introduced like this:

I went to the store and bought groceries including: eggs, milk, bread, and cheese.

This is INCORRECT. Adding the ''including'' makes the stuff before the colon no longer a complete sentence because you wouldn't end a sentence with ''including.'' It also just makes the colon redundant, as the ''including'' already introduces the list.

Besides lists, colons are also used to introduce quotations:

John F. Kennedy inspired young people with his call to national service: ''Ask not what your country can do for you, but what you can do for your country.''

But once again, you only need to use the colon if it follows an independent clause. DO NOT do this:

John F. Kennedy inspired young people to participate in national service when he said: ''Ask not what your country can do for you, but what you can do for your country.''

When preceding a quotation with ''he said'' or some variation, a comma before the quotation is sufficient for the same reasons as with the list: the stuff before the colon can no longer stand on its own, and the introductory phrase makes the colon redundant.

More rarely, a colon is used to introduce a short phrase that is not grammatically connected to the rest of the sentence, known as an appositive. This would be an example of that usage:

Mary had decided on what she wanted to be when she grows up: an astronaut.

This form is rare and should be used sparingly.

Other Uses

Besides its main use with independent clauses, the colon also has some other specialized usages. This includes after the greeting in a business letter:

• To Whom it May Concern:
• Mr. Meyers:

Another specialized usage is between hours and minutes when writing the time in numerical form:

• 12:00 pm
• 4:36 am

A final specialized form is between the chapter and verse when referencing the Bible:

• John 3:16
• Matthew 1:11