A reflex is an automatic response your body makes without you having to think about it. When a doctor taps your knee with that little rubber hammer and your leg kicks forward, that's a reflex. When you touch something hot and your hand jerks back before you even register the pain, that's your body's reflex protecting you.

Many reflexes happen very quickly because the signal can travel through your spinal cord without needing your brain to make a decision first. Your nervous system has built-in shortcuts for emergencies. Blinking when something flies toward your face, pulling your hand away from a sharp object, even catching yourself when you start to fall: these are all reflexes that help keep you safe.

The word also describes quick reactions more generally. A hockey goalie with lightning-fast reflexes can block shots that seem impossible to stop. Video games often test your reflexes by making you respond quickly to sudden changes on screen. Athletes train to improve their reflexes so they can react instantly during competition.

Some reflexes you're born with (like babies automatically grasping anything placed in their palms), while others develop through practice. When something becomes a reflex, it means you do it instantly and naturally, like a musician's fingers finding the right notes without conscious effort.