Regent

In a monarchy, a regent (from Latin regens 'ruling, governing') is a person appointed to execute the office of a monarch temporarily, essentially as a substitute ruler. Regencies may arise for a number of reasons, including the monarch being a minor, ill, absent from the country, or otherwise unavailable. A regent may also be appointed in cases where the throne is vacant, or the identity of the legitimate monarch is disputed. The rule of a regent or regents is called a regency.