noun (n)

• the monthly discharge of blood from the uterus of nonpregnant women from puberty to menopause(noun.process)

  Example:
  The semen begins to appear in males and to be emitted at the same time of life that the catamenia begin to flow in females.
  

  Synonym:
  flow, menses, menstruation, menstruum, period
  

  source: wordnet30
• The monthly courses of women; menstrual discharges; menses.(noun)

  source: webster1913