Chaos (physics)
Etymology
From Greek khaos, "gaping void, formless space," the primordial emptiness before creation in Greek myth. Ordinary use drifted toward "utter disorder." The modern technical sense dates to the 1960s–70s, when Edward Lorenz found that deterministic weather models diverged wildly from nearly identical starting points — the "butterfly effect" at the heart of chaos theory.
noun · /KAY-oss/
In science, the behavior of systems that obey exact rules yet are so sensitive to their starting conditions that their long-term path becomes unpredictable.
What it names
Why some things are genuinely impossible to forecast far ahead even when nothing about them is random — a tiny difference now snowballs into a totally different later.
Example
Trying to plan the exact schedule six months out was hopeless — too much chaos, where one delayed decision reshuffled everything downstream.
Related idea
Chaos is unpredictability that emerges from strict rules; complexity is what arises when many simple parts interact to produce behavior none of them contains alone.
noun · /KAY-oss/
Complete disorder and confusion.
What it names
the everyday sense — utter, tumbling-over-itself mess or pandemonium
Example
When the power failed, the trading floor descended into chaos.
Related idea
The scientific sense is the surprise — that such disorder can hide beneath exact rules; the ancient Greeks used Chaos for the formless void that existed before the ordered cosmos, the very opposite of equilibrium.