Adenomyosis: Pronounced a-den-o- mi-o-sis, this is a common benign condition of the uterus in which the endometrium (the mucous membrane lining the inside of the uterus) grows into the myometrium (the uterine musculature located just outside the endometrium). The endometrium and myometrium under normal circumstances are adjacent to one another, discrete neighbors. In adenomyosis, the endometrium boorishly implants itself in the myometrium. The myometrium may respond to this intrusion with muscular overgrowth. If an island of endometrial tissue is contained and circumscribed within the myometrium, it forms a nodule called an adenomyoma (plural: adenomyomata). Adenomyosis is made up of adeno (gland) + myo (muscle) + osis (a condition of) = a condition of glandular tissue (referring to the endometrium) in the muscle (the myometrium). Adenomyosis goes by several other names including endometriosis interna, endometriosis uterina, adenomyosis uteri and adenomyometritis.