premenstrual syndrome (PMS, pms) [L, prae + menstrualis, monthly, tendere, to stretch] , a syndrome of nervous tension, irritability, weight gain, edema, headache, mastalgia, dysphoria, sleep changes, and lack of coordination occurring during the last few days of the menstrual cycle before the onset of menstruation. Several theories attempt to explain the cause of the syndrome, including nutritional deficiency, stress, hormonal imbalance, and various emotional disorders.
