A colon is a punctuation mark that looks like two dots stacked on top of each other (:). Writers use a colon to introduce something that explains, lists, or expands on what came before it.

For example, you might write: “I need three things from the store: milk, bread, and eggs.” The colon signals that a list is coming. Or you could write: “She had one goal: to win the championship.” Here the colon introduces an explanation of what that goal was.

Think of a colon as a spotlight that points forward, telling readers “pay attention to what comes next.” It's stronger than a comma but not as final as a period. You'll see colons introducing lists, explanations, examples, or important statements. They appear in business letters after greetings (“Dear Sir:”), in time notation (3:45 PM), and in ratios (a 2:1 ratio).

The word colon also refers to a major part of your digestive system: the large intestine, where your body absorbs water and forms waste. It's the same word for two completely unrelated things, one of those quirks of English where context tells you which meaning applies.