A demonstrator is someone who shows others how something works or is done. In a science class, the teacher might ask a student to be the demonstrator for an experiment, carefully performing each step while classmates watch and learn. Store demonstrators show shoppers how to use new kitchen gadgets or toys, making the products easier to understand by actually using them.

The word also refers to someone participating in a public protest or march. These demonstrators gather in groups to show their support for a cause or opposition to a policy. They might carry signs, chant slogans, or march through streets to make their views visible to others. During the American Revolution, demonstrators protested British taxes. In the 1960s, demonstrators marched for civil rights and voting rights.

Both meanings share the same core idea: making something visible and clear to others. Whether showing how a machine operates or showing what you believe through peaceful assembly, a demonstrator puts something on public display. A demonstration (the noun form) is the act of demonstrating, whether it's a science demonstration in the classroom or a peaceful demonstration in the town square.