The words “peace, calm, quiet, silence” have each their own shade of meaning, but it is not easy to define them.
Peace – śānti.
Calm – sthiratā.
Quiet – acañcalatā.
Silence – niścala-nīravatā.
Quiet is a condition in which there is no restlessness or disturbance.
Calm is a still unmoved condition which no disturbance can affect – it is a less negative condition than quiet.
Peace is a still more positive condition; it carries with it a sense of settled and harmonious rest and deliverance.
Silence is a state in which either there is no movement of the mind or vital or else a great stillness which no surface movement can pierce or alter.
Excerpted from this website