Sovereignty
Etymology
From Old French souveraineté, from soverain ("supreme"), which traces to Vulgar Latin superanus, from super ("above"). Notice that the "g" in the English spelling is a false intruder, wrongly inserted by scribes who associated the word with "reign" — the true root is "above," not "rule." The concept hardened into its modern form with the European treaties of the seventeenth century.
noun · /SOV-rin-tee/
The supreme authority of a state to govern itself and its territory without external control.
What it names
It names the foundation stone of the modern state system — the claim to be the final authority within one’s own borders, answerable to no higher power.
Example
The trade pact required each member to surrender a sliver of sovereignty over its own tariffs.
Related idea
Subsidiarity pushes in the opposite direction, arguing decisions should sit at the lowest capable level rather than the top. Sovereignty asserts a single supreme authority; subsidiarity insists that authority hand as much down as it can.