kingdom

A kingdom is a political and geographic entity ruled by a king or queen. Historically, kingdoms were autonomous states often associated with dynasties and defined by territory; sovereignty was usually hereditary or, in some cases, elective. The term is also used in biology to denote a major rank in the classification of life.

In political contexts, kingdoms may be monarchies with varying powers. Constitutional monarchies restrict the monarch’s role to ceremonial duties and symbolic authority, while absolute monarchies vest most or all political power in the crown. Kingdoms have often formed complex relationships with neighboring states, including feudal agreements, alliances, and colonial empires. Present examples include the United Kingdom, the Kingdom of Sweden, and the Kingdom of Saudi Arabia; historical kingdoms include Ancient Egypt, the Kingdom of France, and the Kingdom of Portugal.

In biology, kingdom is the highest traditional rank used to classify organisms, above phyla. Early systems proposed five or six kingdoms, such as Animalia, Plantae, Fungi, Protista, and the Monera (comprising Bacteria and Archaea). Modern genetic data led to a three-domain system that groups life into Bacteria, Archaea, and Eukarya, but many sources still teach the six-kingdom framework. Within the Eukaryota, the kingdoms Plantae, Fungi, and Animalia include the major multicellular lineages; Protista contains many unicellular and some simple multicellular organisms.

Etymology and usage: The term derives from the Old English cyningdom, literally the realm of a king. Beyond politics and biology, kingdom is used in heraldry, world-building, and literature to denote a realm or domain under a ruler.