Other forms: younger; youngest; youngly
Use the adjective young to describe a person who hasn't been alive very long or doesn't have much life experience. You might feel much wiser and more sophisticated than your young cousins — even if you secretly enjoy playing games with them.
As a noun, young generally means "animal babies," like when a mother duck and her young cross the street, though it can also refer collectively to young people: "The young recover so quickly from being sick." When you describe someone as young, you typically mean that they're immature, youthful, or simply not as old as you might expect: "Kids are getting phones so young these days!"