Use a colon [ : ] before a list or an explanation that is preceded by a clause that can stand by itself. You nearly always have a sense of what is going to follow the colon. (Compare the function of a semicolon in this regard.) For example:
- There is only one thing left to do now: confess while you still have time.
- The committee now includes the following people: the mayor, the chief of police, the fire chief, and the chair of the town council.
We often use a colon to separate an independent clause from a quotation (often of a rather formal nature) that the clause introduces:
- The acting director often used her favourite quotation from Shakespeare’s Tempest: “We are such stuff as dreams are made on; and our little life is rounded with a sleep.”
When NOT to Use a Colon
It might be useful to say, also, when we don’t use a colon. Remember that the clause that precedes the colon ought to be able to stand on its own as an independent clause. In other words, we would not use a colon in situations like the following.
- His favorite breakfast cereals were Rice Krispies, Cheerios, and Wheaties. (No colon after were)
- Her usual advice, I remember, was “Keep your head up as you push the ball up the court.” (No colon after was)