[era] n [LL aera, fr. L, counters, pl. of aer-, aes copper, money--more at ore] (1615) 1 a: a fixed point in time from which a series of years is reckoned b: a memorable or important date or event; esp: one that begins a new period in the history of a person or thing
2: a system of chronological notation computed from a given date as basis 3 a: a period identified by some prominent figure or characteristic feature b: a stage in development; esp: one of the four major divisions of geologic time "Paleozoic ~" syn see period