menses

n. The monthly cycle of a woman's sexual fertility and infertility in which an ovum is readied for fertilization and released by the ovary, the lining of the fallopian tubes and uterus engorge with blood and prepare to receive a fertilized ovum, and then both are shed through the openings of the uterus and vagina if no fertilization occurs. This monthly cycle is characteristic of humans and great apes; the females of other species undergo cycles called estrus which have different frequencies and usually do not involve the shedding of blood and the uterine lining. Also called menstruation.