Relative to a period or periods. / Having repeated cycles. / Occurring at regular intervals. / Periodical. / (astronomy) Pertaining to the revolution of a celestial object in its orbit.

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

A publication issued regularly, but less frequently than daily.

Periodic. / Published at regular intervals of more than one day, especially weekly, monthly, or quarterly. / Of, or relating to such a publication.

plural of periodical

plural of periodicity

Recurrence of a woman's periods; menstruation. / The quality of being periodic; tendency to recur at regular intervals.

In a manner that is regular or periodic. / intermittently or recurrently

A length of time. / A period of time in history seen as a single coherent entity; an epoch, era.

(chiefly Canada, US) That's final; that's the end of the matter (analogous to a period ending a sentence); end of story.