periodic

Etymology 1

From French périodique, from Medieval Latin periodicus (“cyclical”), from Latin periodus (“complete sentence, period, circuit”), from Ancient Greek περίοδος (períodos, “cycle, period of time”). Equivalent to period + -ic.

adj

1. Relative to a period or periods.
2. Having repeated cycles.
   There was some laughter, and Roddle was left free to expand his ideas on the periodic visits of cowboys to the town. “Mason Rickets, he had ten big punkins a-sittin' in front of his store, an' them fellers from the Upside-down-F ranch shot 'em up […].” 1899, Stephen Crane, chapter 1, in Twelve O'Clock
3. Occurring at regular intervals.
4. Periodical.
5. (astronomy) Pertaining to the revolution of a celestial object in its orbit.
6. (mathematics, stochastic processes, of a state) For which any return to it must occur in multiples of k time steps, for some k>1.
7. (rhetoric) Having a structure characterized by periodic sentences.

Etymology 2

From per- + iodic.

adj

1. Relating to the highest oxidation state of iodine; of or derived from a periodic acid.