During punctuation exercises in writing classes, some people want to use the dash in place of the colon and vice versa. Well, these two punctuation marks are closely related in their intention, so let's see what the difference is.
A colon follows a lead-in sentence that makes an announcement. For instance:
- Moe Coe should bring the following tools: pliers, hammer, and screwdriver.
- Attending the meeting were as follows: John Conn, Jane Lane, and Sandy Tandy.
Notice how the following or as follows often precedes a colon. But these phrases are not mandatory, as in this example: I like Carson Larson for one reason: he works hard.
A dash also leads into information, but with far greater emphasis. Examples:
- Sue Du did a fine job—as she always does.
- Mark Dark will win—for the third straight year—the Employee of the Year Award.
Let's contrast two closely related sentences to illustrate the difference between the colon and the dash:
- Here is my response: no.
- My response—for the third time—is no.
Do you sense the difference?