An udder is the bag-like organ hanging beneath a cow, goat, or sheep that produces and stores milk. If you've ever seen a dairy cow, you've probably noticed the large, rounded udder between her back legs.

When a mother cow has a calf, her udder fills with milk to feed her baby. On dairy farms, farmers milk cows twice a day by gently squeezing the teats or using special machines attached to the udder. A healthy dairy cow's udder can hold several gallons of milk.

People sometimes confuse udder with utter (which means complete, or to speak), but they're completely different words. Mixing up these words would be a minor mistake, not an utter disaster.