9.4 Punctuation for Style

Notes

Punctuation controls pace and emphasis.

• Semicolon: joins two closely related independent clauses ("The storm passed; the sky cleared") and may precede a transition word followed by a comma ("; however,"). It also separates items in a series that already contain commas.
• Colon: follows a complete independent clause to introduce a list, explanation or quotation. Do not place it directly after a verb or preposition. Wrong: "My favorites are: cats and dogs." Right: "I have two favorites: cats and dogs."
• Dash: sets off an abrupt interruption or emphasis ("The answer—finally—arrived").
• Commas: use for nonrestrictive (extra) information. "My brother, who lives in Ohio, is a nurse." No commas for restrictive information: "The brother who lives in Ohio is a nurse."
• Worked example: "Mark Twain, a Missouri native, wrote about the river." The appositive "a Missouri native" is extra information, so commas set it off.