Astable

Part of speech: adjective

Definitions

1. Describing a circuit or system that has no stable state and switches continuously between two unstable conditions
2. Having no resting equilibrium, so that an electronic or chemical system keeps alternating between states without settling
3. Characterizing a device that oscillates on its own, repeatedly flipping between two output levels without holding either one

Etymology: "Astable" is formed from the prefix "a-" (from Ancient Greek "a-", meaning "not" or "without") and "stable." The Greek prefix entered English through the same route as many other negating prefixes, so the word simply means "not stable." Its base, "stable," has a longer history: it comes from Latin "stabilis," meaning "firm" or "steady," which passed through Old French "estable" and Anglo-Norman "stabel" before reaching Middle English as "stable." "Astable" is best understood as a piecewise doublet of "unstable" and "instable." Those two words both express the same negation, but each reached English by a different path, and "astable" arose alongside them as a third formation built from the same Greek prefix. Its use is largely technical: in electronics, for instance, an astable circuit is one that switches continuously between two states without any stable resting point.

Synonyms: unstable

Antonyms: stable