Current sovereign monarchs (King of Swaziland pictured) are distinguished by their titles and styles, which in most cases are defined by tradition, and guaranteed under the state's constitution. A monarch is the head of a monarchy, a form of government in which a state or polity is ruled by an individual who normally rules for life or until abdication. In political and sociocultural studies, monarchies are normally associated with hereditary rule; most monarchs, in both historical and contemporary contexts, have been born and raised within a royal family. Some monarchies, however, are not hereditary, and the ruler is instead determined through an elective process. Most states only have a single monarch at any given time, although a regent may rule when the monarch is a minor, not present, or otherwise incapable of ruling. (Full list...)