In chronology, a period or series of numbers, which regularly proceed from first to last, and then return to the first, in a perpetual circle. Hence,

The cycle of the moon, or golden number, or Metonic cycle, so called from its inventor Meton, is a period of nineteen years, which being completed, the new and full moons return on the same days of the month.

The cycle of the sun, is a period of twenty eight years, which having elapsed, the dominical or Sunday letters return to their former place, and proceed in the former order, according to the Julian calendar.

Cycle of indiction, a period of fifteen years, at the end of which the Roman emperors imposed an extraordinary tax, to pay the soldiers who were obliged to serve in the army for that period and no longer.

A round of years, or period of time, in which the same course begins again; a periodical space of time.

An imaginary orb or circle in the heavens.