Use Colons After Complete Sentences
Style guides differ significantly, however, when it comes to colons, so the most important thing is to know what style guide you should be following and what rules it recommends. The two main rules that differ are whether you can use a colon after a sentence fragment and whether you capitalize the first word after a colon.
If you don’t follow a specific style guide, you can pick the rules that you like best. Just be sure to use them consistently. Making your own personal style sheet is one way to make it easier to be consistent in the future. If you like a style, write it down.
APA Style: Complete Sentences and Capitalization
I’ll start with the style I like best, which is APA style: the style of the American Psychological Association.
1) In APA style, you use a colon only after a complete introductory clause. In other words, after only something that could stand on its own as a complete sentence.
Squiggly has one dream: becoming a chocolatier. (correct in APA style)
Squiggly bought: chocolate chips, butter, and a spatula. (incorrect in APA style)
2) In APA style, you capitalize the first word after a colon if it’s the start of at least one complete sentence (or of course, if it’s a proper noun).
Squiggly has one dream: He dreams of becoming a chocolatier. (correct in APA style)
Squiggly has one dream: he dreams of becoming a chocolatier. (incorrect in APA style)
So in APA style, you can use a colon only after a complete sentence, and you capitalize the first word after a colon when it’s the start of a complete sentence. See More . . .