A thin, elastic membrane stretched partly or completely across the entrance of the vagina (vestibule). It has no known biological function. An intact hymen has long and erroneously been considered the hallmark of female virginity . The presence or absence of the hymen is no proof of virginity or its opposite; the hymen can be broken in the normal course of physical activities when the body is stretched strenuously, as in athletics, sports or exercises. It may be absent, small, thin and pliant, or, more rarely, tough and dense, completely blocking the vaginal entrance; it varies in size, shape and thickness from woman to woman . If it is too resistant to tearing it may require a small surgical incision, hymenotomy , or even removal, hymenectomy , before vaginal intercourse can take place .