Abstract
It was tried to express sustainability of system by using entropy. Numerical example in linear system was performed in order to verify the expression. It was shown that sustainability could be expressed by stored entropy. Narrow condition of sustainability was that stored entropy velocity was equal to be 0. It was found that time which heat or mass remain in a system was also an index of sustainability. For shorter time, the system has higher possibility of sustainability. Differentiation of entropy production per unit time with respect to time expressed the direction of change in linear system.
