Secession
Etymology
From Latin "secessio," combining "se-" (apart) with "cedere" (to go) — literally “a going apart.” The Romans used it for the plebeians’ dramatic walkouts from the city; in modern usage it denotes a territory’s departure from a nation or union.
noun · /si-SESH-uhn/
The formal withdrawal of a region or group from a larger political body to form its own.
What it names
A specific act of political exit — a part detaching itself intact — rather than the collapse or conquest of a state.
Example
The region’s vote for secession set off a constitutional crisis over whether such an exit was even legal.
Related idea
Distinct from balkanization, which is the messy fragmentation of a state into many small, often hostile pieces; secession is a single deliberate departure, and it aims at forming a new political unit rather than shattering the old one.