To activate means to make something start working or to turn it on. When you activate a new phone, you set it up so it can connect to your network and start making calls. When a teacher activates a fire alarm during a drill, the alarm system springs to life and begins ringing throughout the building.

The word often involves triggering something that was ready and waiting. Activation might mean preparing a gift card before you can use it to buy things, or warming up your muscles before exercise by stretching them. Scientists might activate chemicals in an experiment to start a reaction. Video game players activate special abilities or power-ups to gain temporary advantages.

Sometimes activate describes bringing potential to life: a coach might activate a team's energy with an inspiring speech, or a great teacher might activate a student's curiosity about science. In these cases, something that was dormant or inactive suddenly becomes engaged and working. The opposite of activate is deactivate, which means to turn something off or make it stop working, like deactivating an alarm system when you arrive home.