the quality or state of being unstable; lack of stability or firmness.

the tendency to behave in an unpredictable, changeable, or erratic manner

emotional instability.

noun

balance , constancy , soundness , stability , steadfastness

noun

alternation , anxiety , capriciousness , changeability , changeableness , disequilibrium , disquiet , fickleness , fitfulness , flightiness , fluctuation , fluidity , frailty , hesitation , immaturity , impermanence , inconsistency , inquietude , insecurity , irregularity , irresolution , mutability , oscillation , pliancy , precariousness , restlessness , shakiness , transience , uncertainty , unfixedness , unpredictability , unreliability , unsteadiness , vacillation , variability , volatility , vulnerability , wavering , weakness , ricketiness , wobbliness , insecureness , unstableness , unsureness , apprehensiveness , change , flux , imbalance , incertitude , inconstancy , unbalance