How to Use a Colon in Writing: Lists, Emphasis, Quotations, Ratios, and Titles

The colon (:) serves several functions:

1. Introduce a list – "Required items: test tubes, beakers, pipettes, microscope."
2. Emphasize or explain – "Reason for delay: power outage."
3. Introduce a quotation – "He announced: 'The exam is next week.'"
4. Signal a ratio – "1:2 ratio of flour to water."
5. Separate title and subtitle – "To Kill a Mockingbird: A Novel."
6. Introduce dialogue in scripts – "Character A: 'How are you?'"

No space before colon; one space after (unless followed by quotation mark).