Activation means making something active or turning it on so it can work. When you activate a new phone, you're setting it up so it can connect to the network and do what phones are supposed to do. When scientists activate a chemical reaction, they're making it start happening.

To activate is to change something from inactive (not working) to active (working). Think of it like flipping a switch: before activation, the thing exists but isn't functioning yet.

You might activate a gift card before using it at a store, or activate your muscles by warming up before exercise. In video games, you activate special abilities or power-ups. Your immune system activates when it detects germs, springing into action to fight them off.

Sometimes activation needs a specific trigger. A motion sensor activates lights when you walk into a room. A voice command activates your digital assistant. You can also use activation as a noun: “The activation of the alarm system happens automatically at night.”

The opposite is deactivation, which means turning something off or making it stop working. If you deactivate your account, you're essentially switching it off, though the information might still exist somewhere, just not actively working.