equilibrium

Etymology

From Latin aequilībrium, from equal + lībra (“balance”).

noun

1. The condition of a system in which competing influences are balanced, resulting in no net change.
   1999, The Matrix, Agent Smith speech Every mammal on this planet instinctively develops a natural equilibrium with the surrounding environment but you humans do not. You move to an area and you multiply and multiply until every natural resource is consumed and the only way you can survive is to spread to another area. There is another organism on this planet that follows the same pattern. Do you know what it is? A virus.
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.
   It now appears that the locomotive did not blow up, as was commonly stated at the time, but that the aeroplane flew so low as to come into contact with the dome of the engine, knocking it off. It was the combination of the impact and the uprush of steam that so disturbed the equilibrium of the raider as to cause it to crash. 1943 May and June, “Notes and News: Effective Locomotive "Ack-Ack" Fire”, in Railway Magazine, page 180