period

n.

1. A measure of time

   epoch, time, era, age, eon, interval, duration, term, span, time span, stretch, spell, space, stage, years, days, season, phase, session, while; see also age 3.

2. An end

   limit, conclusion, close; see end 2.

3. A mark of punctuation

   point, full stop, full pause, dot, ending-pitch; see also punctuation.

period is the general term for any portion of time; epoch and era are often used interchangeably to refer to a period marked by radical change, noteworthy developments, etc. an era, or epoch, of great discoveries, but epoch may specifically apply to the beginning of such a new period the steam engine marked an epoch in transportation, while era applies only to the entire period; age is applied to a period identified with some dominant personality or distinctive characteristic the Stone Age; eon refers to an indefinitely long period it all happened eons ago