Use a colon to introduce an explanation, an example, an appositive, a series, a list, or a quotation.

At the baby’s one-month birthday party, Ah Po gave him the Four Valuable Things: ink, inkslab, paper, and brush.

—Maxine Hong Kingston, China Men

Use a colon rather than a comma to introduce a quotation when the lead-in is a complete sentence on its own.

The 2013 State of the Union address ended with a bold challenge: “Well into our third century as a nation, it remains the task of us all…to be the authors of the next great chapter in our American story.”

Colons are also used after salutations in formal letters; with numbers indicating hours, minutes, and seconds; with ratios; with biblical chapters and verses; with titles and subtitles; and in bibliographic entries.

Dear Dr. Ito:

4:59 pm

a ratio of 5:1

Ecclesiastes 3:1

The Joy of Insight: Passions of a Physicist

Boston: Bedford/St. Martin’s, 2013