A queen regnant is a female monarch, equivalent in rank, title and position to a king. She reigns suo jure over a realm known as a kingdom; as opposed to a queen consort, who is married to a reigning king; or a queen regent, who is the guardian of a child monarch and rules pro tempore in the child's stead or instead of her husband who is absent from the realm, be it de jure in sharing power or de facto in ruling alone. A queen regnant is sometimes called a woman king. A princess regnant is a female monarch who reigns suo jure over a principality; an empress regnant is a female monarch who reigns suo jure over an empire.