If a young child is crowned the monarch, a regent is often appointed to govern until the monarch reaches the requisite adult age to rule. Monarchs' actual powers vary from one monarchy to another and in different eras; on one extreme, they may be autocrats (absolute monarchy) wielding genuine sovereignty; on the other they may be ceremonial heads of state who exercise little or no direct power or only reserve powers, with actual authority vested in a parliament or other body (constitutional monarchy).
A monarch can reign in multiple monarchies simultaneously. For example, the monarchy of Canada and the monarchy of the United Kingdom are separate states, but they share the same monarch through personal union.
Monarchs, as such, bear a variety of titles – king or queen, prince or princess (e.g., Sovereign Prince of Monaco), emperor or empress (e.g., Emperor of China, Emperor of Ethiopia, Emperor of Japan, Emperor of India), archduke, duke or grand duke (e.g., Grand Duke of Luxembourg), emir (e.g., Emir of Qatar) or sultan (e.g., Sultan of Oman). Prince is sometimes used as a generic term to refer to any monarch regardless of title, especially in older texts.
A king can also be a queen's husband and a queen can be a king's wife. If both of the couple reign, neither person is generally considered to be a consort.
Monarchy is political or sociocultural in nature, and is generally (but not always) associated with hereditary rule. Most monarchs, both historically and in the present day, have been born and brought up within a royal family (whose rule over a period of time is referred to as a dynasty) and trained for future duties. Different systems of succession have been used, such as proximity of blood (male preference or absolute), primogeniture, agnatic seniority, Salic law, etc. While traditionally most monarchs have been male, female monarchs have also ruled, and the term queen regnant refers to a ruling monarch, as distinct from a queen consort, the wife of a reigning king.