Colons are a helpful punctuation mark, but they can often be used unnecessarily. As a technical editor with ASCENT, I often employ colons to introduce lists or make connections in my writing – but also frequently notice them being used incorrectly. Here are some helpful tips for when to use (and when not to use) colons in your writing.
According to Grammatically Correct by Anne Stilman, “A colon is called for when the first part of a sentence is an introduction, a lead-in, or a build-up to the second part.”
A colon can serve as a bridge between an implied question (the part of the sentence that comes before the colon) and its answer (the part that comes after).
Example: When working on a model, there is one thing you should always do: save your drawing file often!
In this example, the implied question is What should you always do when working on a model? The answer to that question is Save your drawing file often.
A colon can also be used to introduce a list or a series (and should be used if your lead-in sentence includes as follows or the following). Two things to keep in mind: a colon should not follow a sentence fragment and it should not separate a verb from its object (as it does in the incorrect example below). In these cases, the colon is often used unnecessarily and should be removed. You can test this out by removing the colon from the sentence. If the sentence is still grammatical without it, the colon is not needed.
Incorrect: The commands you can use include: move, copy, and mirror.
Correct: The commands you can use include move, copy, and mirror.
You can also rewrite the sentence so that the clause before the colon is a full sentence that can stand on its own, as in the next example.
Correct: The task can be accomplished using three commands: move, copy, and mirror.
There is some debate as to whether a capital letter should be used after a colon if what follows is a complete sentence (otherwise, a lowercase letter should follow a colon). When in doubt, check your style guide and be consistent!
Of course, there are more uses for a colon than what I’ve discussed here. It can be used after a single word when defining a term, to divide a title from a subtitle, or to add emphasis to a sentence, for example. For more tips and tricks on using colons, please feel free to get in touch!
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