An Equilibrium

1. The condition of a system in which competing influences are balanced, resulting in no net change.
2. Mental balance.
3. (chemistry) The state of a reaction in which the rates of the forward and reverse reactions are the same.
4. (physics) The state of a body at rest or in uniform motion in which the resultant of all forces on it is zero.

(a condition of a system in which competing influences are balanced): balance, stability

(mental balance): sanity

(a condition of a system in which competing influences are balanced): disequilibrium, imbalance, instability

(in physics): disequilibrium, non-equilibrium

(mental balance): insanity, instability, madness