Definition · Plain-language
Colon
A colon ( : ) is a punctuation mark used to introduce something that follows — a list, an explanation, a quotation or an example — after a complete statement.
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What a colon introduces
A colon acts like an arrow pointing forward: it tells the reader that what follows will explain, expand or illustrate what came before. Its commonest use is to introduce a list: "The kit contains: bandages, scissors and tape." It also introduces an explanation or summary — "The cause was clear: poor planning." — and longer or formal quotations. A colon can even separate two independent clauses when the second explains the first, in which case some styles capitalise the second clause and others do not. In every case the colon connects a general statement to the specifics that follow it.
The complete-clause rule
A key rule is that the words before a colon should usually be able to stand alone as a complete sentence. This is why "She brought: a map and a torch" is incorrect — "She brought" is not a complete clause, so the colon interrupts the grammar. The correct versions are "She brought a map and a torch" (no colon needed) or "She brought two things: a map and a torch" (now the clause is complete). This rule keeps the colon from splitting a verb from its object or a preposition from its complement. After the colon, what follows need not be a full sentence; it can be a single word, a phrase or a list.
Colon versus semicolon
The colon and semicolon are often confused, but they do opposite jobs. A colon introduces and points forward: the second part explains or completes the first. A semicolon links and balances: it joins two closely related independent clauses of roughly equal weight without a conjunction. Compare "There was one rule: stay together" (colon, introducing an explanation) with "The path was steep; we climbed slowly" (semicolon, joining two equal statements). A quick test: if the second part answers "namely what?" or "such as?", use a colon; if it could stand as its own sentence and simply continues the thought, a semicolon may fit better.
Key facts
At a glance
- Definition: a mark that introduces a list, explanation, quotation or example
- Rule: the words before it should form a complete independent clause
- Points: forward — what follows explains or completes the statement
- After it: may be a word, phrase, list or full clause
- Example: She needed three things: time, money and quiet.
- Not the same as: a semicolon, which links two equal independent clauses
Common misconceptions
What people often get wrong
Often heard: A colon and a semicolon do basically the same thing.
Actually: They are opposites. A colon introduces and points forward to an explanation or list; a semicolon links two closely related independent clauses of equal weight without a conjunction.
Often heard: You can use a colon to introduce a list after any verb, as in "I bought: milk and bread".
Actually: The words before a colon must form a complete clause. "I bought" is incomplete, so write "I bought milk and bread" or "I bought two things: milk and bread".
Often heard: You must always capitalise the first word after a colon.
Actually: Usually you do not. A single word, phrase or list after a colon stays lowercase; styles differ on whether to capitalise a full independent clause, so follow one style consistently.
Going deeper
