realm

Realm is a term with several related meanings, typically describing a domain or area under a ruler’s authority or a defined sphere of activity. In political geography, a realm may refer to a kingdom or other sovereign territory. The word can also denote a broader sense of jurisdiction or influence, as in the realm of law, science, or culture. In everyday usage, a realm often implies both boundaries and sovereignty, but it is not always used to designate a formal state.

Historically, realms were common in monarchies and empires, where rulers governed over contiguous lands and subjects. The word appears in legal and ceremonial language, such as references to “the realm and the commonwealth” in constitutional contexts. Boundaries and legitimacy of a realm could be shaped by treaties, dynastic succession, or conquest.

In fiction and fantasy, realms are frequently depicted as distinct planes, worlds, or dimensions with their own rules, inhabitants, and histories. This sense of a separate, self-contained world popularized many fantasy settings and role-playing games, where heroes travel between realms or realms serve as major settings.

Beyond politics and fiction, realm is used metaphorically to describe a field of study or activity, for example “the realm of mathematics” or “the realm of possibilities.” In technology and computing, the term can denote a defined security domain or authentication realm within networks and software systems.