Sovereignty is the power to rule yourself with nobody above you. A country has sovereignty when its own government makes the final decisions — no foreign state, no outside court, no permission asked for.
It nearly always takes OVER: sovereignty over a territory, sovereignty over its own laws, disputed sovereignty over a group of islands. Politics uses it constantly, in national sovereignty, parliamentary sovereignty (in Britain, parliament has the last word) and popular sovereignty (power comes up from the people). It comes down to the single person too: sovereignty over your own body, over your own choices. Underneath all of these lies the older sense, the rank and authority of a sovereign, a king or a queen. And here is the fine point the arguments turn on: a state can stay independent while handing pieces of its sovereignty to a union by treaty, which is why people disagree furiously about whether any has been lost.
1nounsovereigntyA country's power to govern itself without outside control.
“The treaty was attacked as a surrender of sovereignty.”
2nounideaSupreme authority over a territory or over oneself.
“Both countries claim sovereignty over the islands.”
3nounrankThe rank and authority of a sovereign.
“The crown passed to her, and with it the sovereignty of three kingdoms.”
Sovereignty came through Late Middle English sovereynte from Anglo-Norman sovereyneté and Old French soveraineté, built on soverain. That runs back to Vulgar Latin superānus, 'chief; sovereign', from Latin super, 'above; on top of', and finally to Proto-Indo-European upér, 'above, over'. The whole idea sits inside that one small word: above.
Proto-Indo-European
*upér — above, over
Latin
super — above; on top of
Vulgar Latin
*superānus — chief; sovereign
Old French
soveraineté
Anglo-Norman
sovereyneté
Middle English
sovereynte
English, today
sovereignty
Built from
From Late Middle English sovereynte, souvereyntesoueraynete, soueraynte, souereynte, sovereinete, soverente, sufferaigntie, suffranti, suffrauntè, suffreinte, from Anglo-Norman sovereyneté, soverentee, and Old French soveraineté, souveraineté (modern French souveraineté), from soverain + -té. Soverain is derived from Vulgar Latin superānus (“chief; sovereign”), from Latin super (“above; on top of”) (ultimately from Proto-Indo-European upér (“above, over”)) + -ānus (“suffix meaning ‘of or pertaining to’, usually denoting a relationship of origin, position, or possession”)). The English word is analysable as sovereign + ty.
Etymology from Wiktionary, CC BY-SA