Instability is the quality of not being stable, balanced, or predictable. If you've ever walked out onto a diving board, you've probably noticed its instability — meaning the board bends and bounces as you move.

Instability comes from the Middle French word instabilite, meaning "unsteadiness." Instability can refer to objects that are not stable, but it can also describe unpredictable situations or relationships. For example, you might hear people talk about economic instability. Or if your behavior at school grows erratic and unpredictable, you might be asked to speak to a therapist about your psychological instability.

Definitions of instability
  1. noun
    a lack of balance or state of disequilibrium
    synonyms: imbalance, unbalance
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    a state of equilibrium
    type of:
    loss of equilibrium attributable to an unstable situation in which some forces outweigh others
  2. noun
    the quality or attribute of being unstable and irresolute
    synonyms: unstableness
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    stability, stableness
    the quality or attribute of being firm and steadfast
    the quality of being unstable and insecure
    type of:
    the quality of being unsteady--varying and unpredictable
  3. noun
    unreliability attributable to being unstable
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    type of:
    undependability, undependableness, unreliability, unreliableness
    the trait of not being dependable or reliable
  4. noun
    an unstable order
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    a stable order (especially of society)
    type of:
    a disturbance of the peace or of public order
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