Capital or Lowercase Letter After a Colon?


There's something you need to know: This is correct.

There's something else you need to know: this is also correct.

There's another thing you might find interesting: this is not correct. In fact, it's wrong. 

One more thing that's incorrect: This.

If you're reading this, you probably know that two major editing styles dominate publishing. The Associated Press Stylebook is followed by a lot of news media, and the Chicago Manual of Style governs much of the book and magazine publishing worlds.

When they disagree, readers get conflicting messages about how to write things. Capital letters after colons are a classic example.

The two styles agree that whenever the stuff that follows a colon is less than a complete sentence, start with a lowercase letter.

I saw what he was wearing: jeans and a hoodie.

But they disagree on what to do when the colon introduces a complete sentence.

AP says to start with a capital letter.

I saw him: He was wearing jeans and a hoodie.

Chicago says to start with a lowercase letter if just one sentence is introduced by the colon, but use a capital if it's two sentences or more.

I saw him: he was wearing jeans and a hoodie.

I saw him: He was wearing jeans and a hoodie. His sneakers were Nikes.

Unless you're bound to one of these styles, you can choose whichever method you prefer. Personally, I find AP's rule easier to remember and apply: If it's a full sentence, start with a cap. If not, don't.