The average menstrual cycle is about days long; ovulation occurs on about day

The menstrual cycle is the series of physiological changes that women go through in order to prepare the body for pregnancy. Although it can vary somewhat, the normal menstrual cycle is 28 days long, timed from the first day of bleeding of the current cycle until the first day of bleeding of the next. Ovulation occurs at the midpoint of the cycle, usually on about day 12.

C. a mature ovule of a plant.