Endometriosis is derived from the word “endometrium,” which is the tissue that lines the uterus. Endometriosis is a medical condition characterized by the growth of endometrial tissue outside the uterus. Normally, the uterus lining, known as the endometrium, regenerates during each menstrual cycle in preparation for a potential pregnancy. However, with endometriosis, this tissue begins to grow in other areas of the body. It can develop around the ovaries, fallopian tubes, and even outside the uterine cavity itself.