(historical) The period of Egyptian history from the end of the Third Intermediate Period to the conquest of Egypt by Alexander the Great (the 26th through 31st dynasties), characterized by alternating periods of native and Persian rule.

The length of time during which an activity occurs or a condition remains. It may be measured either in seconds or in millions of years, depending upon the nature of the activity of condition being considered.

(astronomy) A disturbance in the motion of a planet due to its position in its orbit relative to another planet.

plural of periodic inequality

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

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

(history) The age of mass migration of Germanic people in Europe during the early Middle Ages, circa 376 to 800 AD.

plural of periodic month

Synonym of tropical month

The state of a woman too poor to be able to afford sanitary products (tampons, sanitary towels and the like) connected to her period.