Reinforcement means strengthening or supporting something to make it more effective or durable. When workers add steel bars to concrete, they create reinforced concrete that can support much heavier loads than plain concrete could handle alone. When an army sends reinforcements to soldiers in battle, they're adding more troops to strengthen their position.

In everyday life, you might reinforce a cardboard box by taping the corners, or reinforce the knees of your jeans with patches so they last longer. Teachers reinforce learning when they review important concepts multiple times, making the knowledge stick better in students' minds.

The word also has a special meaning in psychology. Positive reinforcement happens when you get something good after doing something, which makes you more likely to do it again. If your parents praise you for cleaning your room, that praise reinforces the cleaning behavior. Negative reinforcement works by removing something unpleasant: when you buckle your seatbelt and that annoying beeping stops, the silence reinforces buckling up.

Whether you're reinforcing a weak bridge, reinforcing good habits, or reinforcing an argument with solid evidence, you're adding strength or support to make something work better.