Synonyms for period:
eon, generation, lastingness, lifetime, longevity, oldness.
aeon, age, course, cycle, date, duration, epoch, era, interim, interval, length, life, measure, season, span, spell.
accomplishment, cessation, checkmate, close, closing, completion, conclusion, culmination, death, demise, ending, exit, expiration, finale, finis, finish, halt, terminal, termination, windup.
cessation, close, closing, closure, conclusion, discontinuance, end, limit, stop, termination.
extent of time (noun)
aeon, age, course, cycle, date, days, duration, epoch, era, generation, interval, measure, season, space, span, spell, stage, stretch, term, time, while, years.
indefinite duration (noun)
eternity, forever, lapse.
point of time (noun)
century, day, decade, hour, microsecond, millennium, millisecond, minute, month, second, semester, term, week, year.
after-school, inning, lights-out, playtime, recess, school day, stopping point, study hall, end of the line, extended school, free period, half-day, school lunch, school night.
assembly, circle, consummation, plateau, run, wind up.
class, lesson, timetable, wrap up.