A hereditary monarchy is one in which the crown is passed down from one member of the royal family to another.
It is historically the most common type of monarchy and remains the dominant form in extant monarchies. It has the advantages of continuity of the concentration of power and wealth and predictability of who controls the means of governance and patronage. Provided that the monarch is competent, not oppressive, and maintains an appropriate royal dignity, it might also offer the stabilizing factors of popular affection for and loyalty to the royal family. The adjudication of what is oppressive, dignified and popular tends to remain in the purvue or the monarch. The main disadvantage is the heir apparent may be physically or temperamentally unfitted to rule. Other disadvantages are the inability of a people to choose their head of state, the ossified distribution of wealth and power across a broad spectrum of society, and the continuation of outmoded religious and social-economic structures mainly for the benefit of the Monarch, their families, and supporters.
Theoretically, when the king or queen of a hereditary monarchy dies or abdicates, the crown is typically passed to the next generation of the family. If no qualified child exists, the crown may pass to a brother, sister, nephew, niece, cousin, or other relative, in accordance with a predefined order of succession, often enshrined in legislation. This process establishes who will be the next monarch beforehand and avoids disputes among members of the royal family. In practice, there is an almost irresistible drive amongst the claimants to the throne. There are few if any monarchies that have not acquired and defended their hold on power through deceit, murder, war and oppression.
In most current monarchies, the typical order of succession is based on a form of primogeniture, but there exist other methods such as seniority, tanistry (in which an heir-apparent is nominated from among qualified candidates) and rotation , which were more common in the past.
Historically, there have been differences in systems of succession, mainly revolving around the question of whether succession is limited to males, or if females are also eligible (historically, the crown often devolved on the eldest male child, as ability to lead an army in battle was a requisite of kingship). Agnatic succession refers to systems where females are neither allowed to succeed nor to transmit succession rights to their male descendants (see Salic Law). An agnate is a kinsman with whom one has a common ancestor by descent in an unbroken male line. Cognatic succession once referred to any succession which allowed both males and females to be heirs, although in modern usage it specifically refers to succession by seniority regardless of sex. Another factor which may be taken into account is the religious affiliation of the candidate or the candidate's spouse, specifically where the monarch also has a religious title or role; for example the British monarch has the title of Supreme Governor of the Church of England.
Elective monarchy can function as hereditary monarchy. A specific type of elective monarchy known as Tanistry limits eligibility to members of the ruling house. But hereditary succession can also occur in practice despite any such legal limitations. For example, if the majority of electors belong to the same house, then they may elect only family members. Or a reigning monarch might have sole power to elect a relative. Many late-medieval countries of Europe were officially elective monarchies, but in fact pseudo-elective; most transitioned into officially hereditary in the early modern age.