From Encyclopedia of Sex and Sexuality
A thin membrane situated at the opening of a woman’s vagina. Its structure is extremely variable; it may be almost entirely absent, form an opening that admits one or two fingers to the vagina, or occasionally form a barrier across the lower edge of the vaginal opening. Despite this variation, the presence of an intact hymen (often called “the maidenhead” in past literature, or “the cherry” in the vernacular) has been taken to be proof of a woman’s virginity in the many traditional cultures that value it. Indeed, “proof” of an intact hymen—sometimes bedsheets stained with chicken blood—is still required of girls and women in some traditional cultures when they marry.
In America and other Western countries it is widely accepted that the hymen may be virtually absent when a woman first experiences intercourse; it may have been stretched or torn as a result of vigorous sports or the insertion of fingers into the vagina, or it may (rarely) have been surgically cut. When a woman’s hymen is intact at the time she first experiences intercourse it will usually be stretched or torn as the male’s penis enters her vagina, possibly causing some pain and minor bleeding. If a woman is worried about this possibility, she can usually stretch the hymen with her fingers or have a physician cut the membrane.
In rare cases, a hymen may actually block the vagina’s opening either totally or nearly so. When girls with such a hymen begin to experience menstruation, the monthly flow of blood from the vagina will be prevented, causing progressive pelvic pain. The problem is usually solved by a surgical incision through the membrane.