People used to believe you could tell if a girl was a virgin by looking to see if her hymen was torn. The hymen is a thin membrane that stretches partway over the opening to the vagina. When a girl has intercourse for the first time—if her hymen is still intact—the membrane usually tears, which can cause some pain and/or light bleeding.

In some cultures, bleeding at first intercourse is still considered solid proof that a girl is a virgin. But, we know a hymen can be torn as a woman’s body grows and develops. Bike riding or playing certain sports, like gymnastics, may also cause the hymen to tear. Some girls are born without a hymen. And, it’s very common for some girls not to bleed at all the first time they have sexual intercourse.

It’s impossible for a doctor to examine a girl and tell if she is a virgin. If she still as an intact hymen, then she probably has not had vaginal intercourse. But, if she has no hymen, there could be many reasons for this.

A lot of discussion about virginity is about girls. What about the guys? It is also impossible to tell if a guy is a virgin. Even a doctor can't tell. Only the guy knows for sure.