To spoil means to ruin or damage something, often something good. When milk spoils, bacteria make it sour and unsafe to drink. When rain spoils a picnic, it forces everyone inside. When someone spoils the ending of a movie by revealing what happens, they wreck the surprise that makes watching it exciting.

The word can describe physical damage: fruit spoils when it sits too long and becomes rotten. But it also describes ruining experiences or opportunities. A single complaint can spoil someone's good mood. One player refusing to follow the rules can spoil the game for everyone else.

Spoil also means to treat someone with excessive kindness or generosity, especially in ways that might not be good for them. Parents might spoil a child by giving them everything they want and never saying no. Grandparents often enjoy spoiling their grandchildren with treats and gifts. A spoiled child has been given so much without earning it that they expect everything to go their way.

As a noun, spoils are valuable things taken as prizes, especially after a victory. When armies conquered cities in ancient times, they took valuable items as spoils of war. Today, we still use this phrase to describe the rewards that come from winning any kind of competition or conflict.