Rot means to decay or break down, usually because of bacteria, fungi, or moisture. When food rots, it becomes soft, smelly, and inedible: a forgotten apple in your backpack might start to rot and turn brown and mushy. Wood rots when it stays wet too long, becoming weak and crumbly instead of solid and strong.

The process of rotting is nature's way of recycling. Fallen leaves rot on the forest floor, breaking down into rich soil that feeds new plants. Gardeners create compost piles where vegetable scraps deliberately rot into fertilizer. But rot becomes a problem when it happens to things we want to keep: rotting teeth develop cavities, rotting floorboards become dangerous, and rotting fruit attracts flies.

Rot can also be a noun, meaning the decay itself, or the damage it causes. You might hear about root rot in plants or dry rot in wood.

The word also describes things falling apart in other ways. Someone might say a friendship started to rot when lies and broken promises damaged the trust between two people. A neighborhood might rot when buildings fall into disrepair and people stop taking care of their community. In these cases, rot suggests something once healthy or strong gradually weakening until it can no longer serve its purpose.