the continuum of experience in which events pass from the past through the present to the future

a daily cycle of activity observed in many living organisms

the time in a woman's life in which the menstrual cycle ends

a period in a man's life corresponding to menopause

the period during which an embryo develops (about 266 days in humans)

(neurology) the time after a neuron fires or a muscle fiber contracts during which a stimulus will not evoke a response