An activator is something that causes a process to begin or makes something start working. In science, an activator might be a chemical that triggers a reaction, like adding yeast to dough, which activates the rising process that makes bread fluffy. In your body, certain proteins act as activators, switching on important biological processes when needed.

The word appears in everyday contexts too. A motion sensor can act as an activator that turns on lights when you enter a room. Some toys have voice activators that make them respond when you speak. In chemistry class, you might add an activator solution that causes a color change in an experiment.

Think of an activator as the thing that gets the ball rolling. When you press a button to start a blender, pressing the button is the activator. When a coach gives an inspiring speech that fires up the team before a big game, that speech acts as an activator for the players' energy and focus. The key idea is that an activator sets something in motion that was previously still, dormant, or waiting to begin.