/ ˈɪərə; NAmE ˈɪrə; ˈerə/ noun
1.
a period of time, usually in history, that is different from other periods because of particular characteristics or events :
the Victorian / modern / post-war era
When she left the firm, it was the end of an era (= things were different after that) .
2.
( geology ) a length of time which is a division of an aeon
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WORD ORIGIN
mid 17th cent.: from late Latin aera , denoting a number used as a basis of reckoning, an epoch from which time is reckoned, plural of aes , aer- money, counter.