Colons and semicolons are tricky marks of punctuation. I see them misused all the time. I also see quite a few books (and student papers) that don’t contain a single colon or semicolon, which suggests the writer isn’t sure how to use them correctly and is just avoiding the whole issue.

Colons

Colons are used within sentences. Typically, they mark the transition between a general statement and a specific elaboration. That elaboration might be a definition, an example, a more detailed clarification, a list, or a quotation. Here are some examples:

1. Sally’s purse contained some weird items: a dried up bottle of White-Out, a can of baked beans, an Elmo doll, and nine old toenail clippings. (assertion: list)
2. Many people misuse the word “nauseous”: rather than being synonymous with “nauseated,” “nauseous” means “nausea inducing.” (assertion: definition)
3. “Nauseous” means “nausea inducing”: “I saw a nauseous car accident on the way home from work.” (assertion: example)
4. Trapped by his own lies, Bill Clinton began to sound rather silly: “It depends upon what the meaning of the word ‘is’ is.” (assertion: supporting quotation)

A semicolon wouldn’t be appropriate in situations like these. Rather than separating the general from the specific within a sentence, a semicolon joins what could be two complete and separate sentences into one. But more on that in my next MM, which will focus on semicolons.

Now There’s No Going Back

One more point about colons before I leave them behind: when you include one in a sentence, it forms a sort of syntactical wall. You can’t go back to the line of syntax you had before the colon and pick it back up again. Here’s an example of this kind of error, which I see quite a bit:

Sally’s purse contained some weird items: a dried up bottle of White-Out, a can of baked beans, an Elmo doll, and nine old toenail clippings, all of which suggested she was a bit of a pack rat.

The main thrust of the above sentence goes like this:

Sally’s purse contained some weird items, all of which suggested she was a bit of a pack rat.

The list “a dried up bottle of White-Out, a can of baked beans, an Elmo doll, and nine old toenail clippings” is an aside. What the writer wants to do is take a break in the main thrust of the sentence, offer the supporting evidence, and then go back to the main point, which is Sally’s pack-rattiness. But there’s no “going back” after a colon. When you put a colon in, whatever came before it is finished, and later parts of the sentence can’t pick it back up.

Instead, the author needs to use dashes or parentheses:

Sally’s purse contained some weird items — a dried up bottle of White-Out, a can of baked beans, an Elmo doll, and nine old toenail clippings — all of which suggested she was a bit of a pack rat.

Sally’s purse contained some weird items (a dried up bottle of White-Out, a can of baked beans, an Elmo doll, and nine old toenail clippings), all of which suggested she was a bit of a pack rat.

Colons and Caps

You will see some people capitalizing the first letter after a colon. Personally, I think that’s weird, even if what comes after the colon could stand alone as a complete sentence. Could, schmould, you know? You chose not to make it stand alone, so it’s not a sentence, even if it could’ve been.