5. Mature age; especially, the time of life at which one attains full personal rights and capacities; as, to come of age; he (or she) is of age. Abbott. In the United States, both males and females are of age when twenty-one years old.
6. The time of life at which some particular power or capacity is understood to become vested; as, the age of consent; the age of discretion. Abbott.
7. A particular period of time in history, as distinguished from others; as, the golden age, the age of Pericles. "The spirit of the age." Prescott.
Truth, in some age or other, will find her witness.
Milton.
Archeological ages are designated as three: The Stone age (the early and the later stone age, called paleolithic and neolithic), the Bronze age, and the Iron age. During the Age of Stone man is supposed to have employed stone for weapons and implements.
See Augustan, Brazen, Golden, Heroic, Middle.