Two Marks, Two Jobs

The colon and the semicolon are among the most misused punctuation marks in English. Many writers avoid both entirely, relying on commas, dashes, and periods instead. But colons and semicolons do things no other mark can do, and using them correctly signals control over your prose.

The Colon: Here Comes What I Promised

A colon says "what follows explains or fulfills what came before." Think of it as an arrow pointing forward. The clause before the colon sets up an expectation, and the text after the colon delivers on it.

  • "She packed three things: a notebook, a pen, and her courage."
  • "The verdict was clear: he had been right all along."
  • "Lincoln's words still resonate: 'Government of the people, by the people, for the people.'"

The critical rule: the text before a colon must be a complete sentence. "She packed: a notebook, a pen, and her courage" is wrong because "She packed" is not a complete thought on its own. Add an object, "She packed three things:", and it works.

The Semicolon: Two Ideas, One Thought

A semicolon connects two independent clauses that are closely related. Each clause could stand alone as a sentence, but the writer wants to show that they belong together, that the second thought flows from or complements the first.

  • "The storm knocked out power for six hours; the neighborhood ran on candles and conversation."
  • "He did not expect to win; he entered the contest for the practice."

The test is simple: can each side of the semicolon stand alone as a sentence? If yes, a semicolon is valid. If either side is a fragment, use a different mark.

  • "The conference included speakers from Austin, Texas; Portland, Oregon; and Bangor, Maine."

Without semicolons, that sentence becomes a confusing string of commas.

Common Mistakes

Using a semicolon before "because" or "since." These subordinating conjunctions create dependent clauses, not independent ones. Use a comma instead.

Using a colon after an incomplete sentence. "My favorite foods are: pasta, rice, and bread" is wrong. Remove the colon or restructure: "My favorite foods are pasta, rice, and bread" or "I have three favorite foods: pasta, rice, and bread."

Using a semicolon where a colon belongs. If the second clause explains or specifies the first, a colon is usually better. If the two clauses are parallel or contrasting, a semicolon fits.

The Simplest Advice

When in doubt, use a period. Two short sentences are always clear. But when you want to show a tighter relationship between ideas, these two marks give you precision that periods and commas cannot.