Prevention means stopping something bad from happening before it starts. When you wash your hands before eating, you're practicing disease prevention by keeping germs from making you sick. When a city builds flood barriers, that's flood prevention. When you study throughout the semester instead of cramming at the last minute, you're using prevention to avoid the stress and poor performance that can come with procrastination.

Prevention requires thinking ahead. A doctor might recommend exercise and healthy eating for disease prevention instead of waiting until someone gets sick to treat them. A fire drill at school is prevention in action: practicing what to do so that if a real emergency happens, everyone knows how to stay safe.

The old saying “an ounce of prevention is worth a pound of cure” captures why this matters: it's much easier to stop problems before they start than to fix them afterward. Brushing your teeth twice a day takes two minutes, but fixing a cavity can take hours at the dentist. Prevention takes effort and planning, but it saves you from much bigger troubles down the road.

The related word preventive (sometimes spelled preventative) describes actions taken to prevent something: preventive medicine, preventive maintenance on a car, or preventive measures against burglary.