What is the difference between dyspareunia and vaginismus?

Good question: Dyspareunia is pain in the pevlic area associated with intercourse not due to some other primary pain. Vagnismus is not well defined, but is believed to be involuntary pelvic muscle contraction (even though studies have not corroborated this) which prevents penetration. Vaginismus is always associated with dyspareunia but not the other way around.