A baby is a very young child, typically from birth until around age one or two, before they learn to walk and talk well. Babies need constant care: they can't feed themselves, walk, or communicate with words. Instead, they cry to let adults know they're hungry, tired, uncomfortable, or need attention.

Taking care of a baby requires enormous patience and responsibility. Parents feed babies every few hours, change their diapers, help them sleep, and watch them constantly to keep them safe. This demanding work continues day and night for months, which is why new parents often feel exhausted.

The word baby can also describe the youngest member of a family or group, like the baby of the family, even if that person is no longer an infant. As a verb, baby can mean treating someone too gently or protectively, as in “don't baby him” when someone is old enough to handle things on their own.

You'll also hear baby used for young animals, though many have specific names: a baby dog is a puppy, a baby cat is a kitten, and a baby cow is a calf. But if you're unsure of the specific term, calling a young animal a baby is perfectly fine, and everyone will understand what you mean.