Phase Transition
Etymology
A physics term joining "phase" — from Greek "phasis" ("appearance") — with "transition," from Latin "transire" ("to go across"). It names the shifts between solid, liquid, gas, and beyond; social scientists borrow it for tipping-point changes in crowds, markets, and opinion.
noun phrase · /FAYZ tran-ZISH-un/
A sudden, wholesale change in the state of matter — like water freezing or boiling — that happens at a critical point.
What it names
A powerful model for abrupt, qualitative change: systems can absorb steady pressure with little visible effect, then flip to an entirely new state all at once.
Example
Public tolerance held for months, then hit a phase transition and turned into open protest almost overnight.
Related idea
Where a threshold is merely the line you cross, a phase transition is what happens at that line — the abrupt reorganization into a fundamentally different state, not just a step past a marker.