Colons

Lace up your grammar gloves, step into the ring, and brace yourself for Punctuation, Round II. With the fearsome semicolon now a familiar friend, we move on to the slightly better understood (but still somewhat confusing) colon.

Colons have several uses, but all of them follow a basic rule: a colon follows an independent clause (or a full, stand-alone sentence) to provide an example or additional, needed information. Consider that last sentence. In the initial independent clause, I said there was a “basic rule”; after the colon, I explained what that basic rule was.

You might recall that semicolons can also join together two full sentences that are closely related; colons tend to do this a little more specifically. A semicolon can join two related sentences to make writing flow more smoothly, but a colon introduces information the reader needs to fully understand the initial sentence. For example, you might have felt lost and a little annoyed if someone mentioned a “basic rule” and never told you what it was.

Although colons can join full sentences, they can also introduce other things: a single word, a non-sentence phrase, or a list of items. When a colon introduces a non-sentence phrase or a single word, there is usually one intended purpose: dramatic effect.

To capture the remaining uses for colons, I’ll borrow this quote from Strunk and White: “The colon has certain functions of form: to follow the salutation of a formal letter, to separate hour from minute in a notation of time, and to separate the title of a work from its subtitle or a Bible chapter from a verse.” Additionally, a colon can also precede a long quotation after an introductory sentence. 

In the above examples, you may notice that the colon never directly follows a verb. More specifically, it would be incorrect to write, “The rule for colon use is: a colon follows…” or, “Other things that colons can precede are: a single word, a long…” The initial phrases in these examples are not full sentences, so there’s no need for a colon.

With an overview of colons behind us, hopefully you see how helpful those double dots can be. When it comes to providing additional information or clarifying your point, the colon is king. Though it’s always important to be clear, never forget the most important moral the colon has to offer: we can all do with a little more dramatic effect.

Source: 1, 2, 3