Definition of: era

(ir′ə, ē′rə) noun
1. A historical period or reckoning of years, dating from some important event or fixed point of time; a period running from a fixed epoch established as the basis of a chronology.
2. A period of time characterized by some coextensive phenomenon or order of things, or social, iatellectual, or physical conditions, etc.
3. A date or event from which time is reckoned; a time or age marked by a remarkable event; the beginning of a period; an epoch: the Christian era.
4. Geol. A division of geological history of highest rank: the Cenozoic era. See chart under GEOLOGY. [<LL aera counters; orig. plural of aes brass, money]