An allusion is a brief reference to something well-known: a person, place, event, book, or story that the writer or speaker expects you to recognize. When someone says “Don't be a Scrooge,” they're making an allusion to Charles Dickens's character from A Christmas Carol, the miser who hates generosity. The speaker doesn't explain who Scrooge is because they assume you already know.

Allusions work like shortcuts in communication. Instead of explaining that someone is being greedy and cold-hearted, you can simply say “Stop being such a Scrooge” and anyone familiar with the story immediately understands. Writers use allusions to Greek myths, Bible stories, historical events, and famous books to add layers of meaning without lengthy explanations.

The key to an allusion is that it's indirect. If you write “Like Ebenezer Scrooge, who refused to give Bob Cratchit a raise and hated Christmas,” you're no longer making an allusion: you're making a direct reference or comparison. An allusion trusts the reader to make the connection.

Be careful not to confuse allusion with illusion. An illusion is something that tricks your senses or mind, like a magic trick or a mirage in the desert. An allusion is a reference to something real that already exists in stories, history, or culture.