recurring at intervals of time

periodic revivals of an interest in handicrafts.

occurring or appearing at regular intervals

periodic visits of a mail steamer to an island.

repeated at irregular intervals; intermittent

periodic outbreaks of the disease.

Physics . recurring at equal intervals of time.

Mathematics . (of a function) having a graph that repeats after a fixed interval (period) of the independent variable.

Astronomy .

characterized by a series of successive circuits or revolutions, as the motion of a planet or satellite.

of or pertaining to a period, as of the revolution of a heavenly body.

pertaining to or characterized by rhetorical periods, or periodic sentences.

adverb

betimes , occasionally , sometimes , sporadically