Preventative means designed to stop something bad from happening before it starts. When you get a flu shot, that's preventative medicine because you're trying to prevent yourself from getting sick. When a soccer goalie practices diving saves during the week, that's preventative work to stop goals during the game.

You might also see this word spelled preventive, which means exactly the same thing. Both are correct, though preventive is slightly more common in formal writing.

Think of preventative measures as the opposite of fixing problems after they occur. Brushing your teeth is preventative care against cavities. Studying throughout the school year is preventative work against cramming before big tests. A smoke alarm is a preventative device that warns you of danger before a fire spreads.

The key idea is acting early, before trouble arrives. A ship captain who checks the weather forecast is taking preventative action against sailing into a storm. A student who organizes their backpack each night is doing preventative work against forgetting homework in the morning. Preventative thinking means asking yourself: “What can I do now to avoid problems later?”