A brook is a small, natural stream of fresh water. Picture a narrow ribbon of water gurgling over rocks and pebbles, small enough that you could probably jump across it in most places. Brooks are smaller than rivers, and you often find them flowing through woods or meadows, creating peaceful sounds as the water tumbles along.

The water in a brook moves continuously, fed by underground springs, melting snow, or rainfall from higher ground. Many brooks eventually flow into larger streams and rivers. Animals come to brooks to drink, and if you look closely at the clear, shallow water, you might spot small fish, tadpoles, or insects skating across the surface.

The word brook can also be used as a verb meaning to tolerate or accept something, though this usage is fairly formal and old-fashioned. When someone says they “will brook no interference,” they mean they won't accept or allow anyone to interfere with what they're doing. You're much more likely to encounter brook as a noun referring to that small, bubbling stream where you might spot minnows or skip stones on a summer afternoon.