PMS stands for Premenstrual Syndrome. It's a way that a woman's body get's rid of some excess things. What happens is that your stomach/bladder/womb (I don't know exactly what) gets rid of a thin layer of blood that lines it, because it is not needed (and is only needed when you're pregnant). It does this every month, for a bout a week, and causes stomach cramps, bloating, and a sudden craving for chocolate, 或者 other comfort foods. That is about the onnly way I can put that. Sorry if I offended any other girls 由 typing this.
PMS stands for premenstrual Sydrome AKA period it's occurs every 月 for girls and it's sucks because blood comes out of our 'area' it usually last for 7 days (depending on genes) moodiest occurs usually because of the menstrual cramps.
