Answer:
In chemistry:
Chemical equilibrium is defined as the condition in the course of a reversible chemical reaction in which no net change in the amounts of reactants and products occurs
In physics:
Equilibrium is defined as the condition of a system when neither its state of motion nor its internal energy state tends to change with time.
A simple mechanical body is said to be in equilibrium if it experiences neither linear acceleration nor angular acceleration; unless it is disturbed by an outside force, it will continue in that condition indefinitely.