Era, n.; pl. Eras.
Etymology: [LL. aera an era, in earlier usage, the items of an account, counters, pl. of aes, aeris, brass, money. See Ore.]
1. A fixed point of time, usually an epoch, from which a series of years is reckoned. The foundation of Solomon's temple is conjectured by Ideler to have been an era. R. S. Poole.
2. A period of time reckoned from some particular date or epoch; a succession of years dating from some important event; as, the era of Alexander; the era of Christ, or the Christian era (see under Christian). The first century of our era. M. Arnold.
3. A period of time in which a new order of things prevails; a signal stage of history; an epoch. Painting may truly be said to have opened the new era of culture. J. A. Symonds.
Syn. -- Epoch; time; date; period; age; dispensation. See Epoch.
Shades of meaning
Fernald has no entry of its own for era; he lists it under time.
He lists it without comment; the entries above explain its neighbors.