Use Colons Correctly

In formal writing, the colon is used only as a means of signaling that what follows is a list, definition, explanation, or concise summary of what had gone before. The colon usually follows an independent clause, and it will be frequently be accompanied by a reinforcing expression like the following, as follows, or namely, or by an explicit demonstrative like this.

• CORRECT: Your instructions are as follows: Read the passage carefully, answer the questions on the last page, and turn over your answer sheet.
• CORRECT: This is what I found in the refrigerator: a moldy lime, half a bottle of stale soda, and a jar of peanut butter.

Be careful not to put a colon between a verb and its direct object.

• INCORRECT: I want: a slice of pizza and a small green salad.
• CORRECT: This is what I want: a slice of pizza and a small green salad. (The colon serves to announce that a list is forthcoming.)
• CORRECT: I don't want much for lunch: just a slice of pizza and a small green salad. (Here what follows the colon defines what don't want much means.)

Context will occasionally make clear that a second independent clause is closely linked to its predecessor, even without an explicit expression like those used above. Here, too, a colon is appropriate, although a period will always be correct too.

• CORRECT: We were aghast: The "charming country inn" that had been advertised in such glowing terms proved to be a leaking cabin full of mosquitoes.