What does bistable mean?
Bistable describes any device or system that has two stable states and can rest indefinitely in either one until something external pushes it to switch. The word belongs mainly to electronics and physics: a bistable circuit — most famously the flip-flop, or bistable multivibrator — stays high or low on command, which is exactly what lets digital hardware remember information, one bit at a time. The idea extends beyond electronics to mechanics, chemistry, and optics wherever a system offers two equally lasting equilibria, such as a light switch that clicks firmly on or off, a shape-memory alloy with two rest configurations, or an optically bistable material. Its natural opposites are monostable (one stable state, always returning to it) and astable (no stable states, oscillating forever). Though rarely heard outside technical contexts, bistable captures a concept fundamental to memory, switching, and storage throughout modern technology, making it a quietly essential piece of the vocabulary behind every digital device.
adjectiveHaving two stable states; capable of resting indefinitely in either of two distinct configurations until an external input causes it to switch. The term is used chiefly in electronics, physics, and systems theory, especially of devices such as the bistable multivibrator (flip-flop) that store one bit of information.
- (of a system, device, or circuit) having two stable states between which it can be switched and in either of which it can remain indefinitely
- (more generally, of physical or chemical systems) possessing two distinct stable equilibria, as in bistable molecules or optical bistability
"The circuit's bistable element holds its output high or low until a trigger pulse flips it to the other state."
"The flip-flop is the classic bistable circuit, storing a single bit until it receives a pulse to change state."
"Researchers exploited the bistable behavior of the polymer film, which snapped between two shapes depending on temperature."
Every bit your computer has ever stored traces back to a humble bistable circuit — a switch that remembers which of two doors you left open.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of bistable
The word bistable is formed from the Latin-derived prefix bi-, meaning 'two' (as in bicycle and binary), combined with 'stable', from Latin stabilis, meaning 'firm' or 'steadfast'. It arose as a technical coinage within twentieth-century electronics, describing circuits such as the multivibrator that possess two steady operating states, and later spread into physics and chemistry for systems with two stable equilibria. It shares the root stabilis with words such as stability, stabilize, and establish.
Related word forms
How bistable is actually used
Bistable is a technical term, found almost exclusively in electronics, engineering, physics, chemistry, and related scientific writing; it is rare in everyday speech. It is typically attributive (bistable circuit, bistable device) but also functions predicatively (the system is bistable). The corresponding abstract noun is bistability.
Easily confused with bistable
A monostable device has only one stable state and returns to it automatically after being triggered, whereas a bistable device remains in whichever of its two states it was last set to.
An astable circuit has no stable states and oscillates continuously, unlike a bistable circuit, which rests indefinitely in either of two states.