A subdivision of the Devonian system of America

(epidemiology) The time elapsed between an exposure to a pathogenic organism, a chemical or radiation, and the appearance of signs and symptoms.

(astronomy) The apparent orbital period of a planet as seen from Earth.

(astronomy) sidereal orbital period / (astronomy) sidereal rotation period

(historical) The history of Japan covering the years from AD 710 to 794. Empress Gemmei established the capital of Heijō-kyō (present-day Nara).

Sexual intercourse during menstruation.

(politics, government) In Canadian federal and provincial parliaments, a period of regularly scheduled time in the lower chamber during which members of the official opposition party and other members may direct questions to the prime minister and to cabinet ministers concerning affairs of state.

Alternative form of Question Period

(chemistry) The principle that chemical properties of the elements are periodic functions of their atomic numbers

(biology) The period, after excitation, during which a membrane recovers its polarization and is not able to respond to a second stimulus.