Age means how long someone or something has been alive or in existence. You might say “I'm ten years old” to tell someone your age, or notice that an ancient oak tree has an age of three hundred years. Age is measured in time: minutes for a newborn puppy, years for a person, centuries for a cathedral, or even millions of years for dinosaur fossils.

As a verb, to age means to grow older or to make something look older. Cheesemakers age certain cheeses in caves for months or years to develop their flavor. Wood ages in the sun, turning gray and weathered. People age throughout their lives, gaining experience and wisdom along with wrinkles and gray hair.

Age also refers to a particular period in history. The Stone Age describes when humans used stone tools, while the Ice Age was when glaciers covered much of Earth. When historians talk about the age of exploration or the digital age, they're describing eras defined by what mattered most during those times.

Sometimes people use age to mean being old enough for something. You might not be of age to drive a car yet, meaning you haven't reached the legal age of sixteen or eighteen, depending on where you live. The phrase come of age means reaching adulthood or maturity.