Should You Capitalize the First Word of a Sentence after a Colon?

My previous post titled “How to Use Colons” explains how colons can be used to preface run-in and vertical lists, introduce quotations, conclude salutations, and link titles with subtitles. Colons can also connect tightly coupled sentences, such as those with a cause-and-effect or problem–solution relationship. Today’s post tackles the question of whether you should capitalize the first word of a sentence after a colon.

This topic deserves its own post because there is no “absolute” answer. Instead, the decision to use a capital or lowercase letter will depend on your style guide. And as usual, the style guides don’t always agree!

Here is a summary of the recommendations provided by three of our primary style guides: The Chicago Manual of Style (Chicago), The Associated Press Stylebook (AP), and the Publication Manual of the American Psychological Association (APA).

The Chicago Manual of Style: Chicago recommends lowercasing the first word of a sentence after a colon unless the colon precedes multiple closely related sentences, in which case the first word should be capitalized.¹

The train is scheduled to arrive forty-five minutes late: a herd of cattle is crossing the tracks.

The train is scheduled to arrive forty-five minutes late: A herd of cattle is crossing the tracks. The cows are taking their time.

The Associated Press Stylebook and the Publication Manual of the American Psychological Association: AP and APA both suggest capitalizing the first word of any complete sentence following a colon.²

The writer debated the future of her long-unfinished work: Should she finish the novel or start a new one?

If you haven’t chosen a style guide and are wondering which one to follow, I always recommend The Chicago Manual of Style for general business writing. Check out my post “Alternative Style Manuals” for more information on these guides and several additional options.

References

1. The Chicago Manual of Style, 17th ed. (Chicago: University of Chicago Press, 2017), 6.63.

2. The Associated Press Stylebook 2019 (New York: The Associated Press, 2019), 323; Publication Manual of the American Psychological Association, 6th ed. (Washington, DC: American Psychological Association, 2010), 90.