(psychology, biology) A maturational stage in the lifespan of an organism during which the nervous system is especially sensitive to certain environmental stimuli.

(astronomy) The roughly 1460-year period of time between successive alignments of the first days of the Egyptian civil calendar and the observational Sothic year.

a work of the screen that evokes a particular historical period

(communism, history) According to an obsolete theory, a period shortly after the Great Depression in which capitalism would be marked by further crises and then soon collapse.

A subdivision of the Devonian system of America

Pain felt in the abdomen during menstruation.

(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.

Synonym of time period

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.