Personal union

A political arrangement in which two or more states share one monarch while retaining separate governments, laws, and institutions.

Monarch: A sovereign ruler who holds a hereditary or elected royal title. The monarch is the shared head of state linking otherwise separate political communities.
Polish–Lithuanian Union: A series of agreements linking the Kingdom of Poland and the Grand Duchy of Lithuania, beginning in 1385. The early arrangement joined the crowns while the two polities initially kept separate institutions.
Real union: An association of states sharing a monarch and some common institutions while retaining separate statehood. Real unions add institutional links that a purely personal union need not have.
War of the Spanish Succession: A European conflict from 1701 to 1714 over the succession to the Spanish throne and the balance of power. The prospect of France and Spain sharing a monarch drove other powers to resist the union.
Crown (government): The state authority and institutions exercised in the name of a monarch. Separate crowns can remain institutionally distinct even when one person holds them.
Union of the Crowns: The 1603 accession of James VI of Scotland to the English throne, placing both crowns on one monarch. England and Scotland shared James while remaining separate kingdoms for more than a century.
Federation: A political system that divides sovereignty between a central government and constituent units. A federation shares governing authority through institutions, not simply through one monarch.
Act of Union 1707: The legislation that united the kingdoms of England and Scotland as the Kingdom of Great Britain. The end of the English and Scottish crown union came through a parliamentary merger.
Union state: A single sovereign state formed by combining previously distinct political units. Unlike a personal union, a union state consolidates sovereignty within one state.
Kalmar Union: A union of Denmark, Norway, and Sweden under a common monarch, established in 1397. It combined a shared monarch with continuing divisions among the Nordic kingdoms.

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