Vagina: The female organ used for sexual intercourse.  The vagina is also the birth canal.  This is also the tube which joins the uterus to the outside of the body. See related article Teen Girls' Development

Vaginal Sex: When a penis penetrates the vagina.

Violence: Deliberate actions to cause harm/death to persons or animals.  This would also include property damage or destruction. See related article on Teen Violence

Virgin: A person who has never had sexual intercourse.  For males there is no physical signs, for a female the hymen is broken.