A clapper is the part inside a bell that strikes against the sides to make it ring. When you swing a bell, the clapper (usually a metal piece hanging in the center) bangs against the bell's walls, creating that clear ringing sound. Without the clapper, even the most beautiful bell would stay silent.

Church bells, school bells, and handheld bells all have clappers. The Liberty Bell's famous crack actually changed how its clapper struck the metal, which altered the bell's tone. Some bells have clappers you can pull with a rope, while others swing freely when the whole bell moves.

The word can also refer to someone who claps, though this meaning is less common. You might see it in old descriptions of theater audiences: “The clappers in the balcony gave the performance a standing ovation.”

Interestingly, a clapperboard (often just called a clapper) is that hinged slate you see in movies where someone snaps the top piece down while saying “Scene 12, take 3!” The sharp clapping sound helps film editors match the picture with the separately recorded audio.