A curtain is a piece of fabric that hangs in front of something to cover it or block it from view. Most commonly, curtains hang over windows to control light, provide privacy, or add decoration to a room. You might close your bedroom curtains at night so neighbors can't see in, or pull them open in the morning to let sunshine flood the room.

In theaters, a large curtain hangs across the front of the stage. Before a play begins, the curtain rises (or opens) to reveal the actors and scenery. When the performance ends, the curtain falls or closes. This theatrical curtain is so important that people often say “curtain call” to describe the moment when actors return to the stage to receive applause at the end of a show.

The word can also describe something that blocks your view or understanding, like when fog creates a curtain of mist across a lake. During the Cold War, people spoke of an “Iron Curtain” separating Communist Eastern Europe from democratic Western Europe, because information and people couldn't easily pass between them, as if a heavy barrier had dropped between the two sides.