Q. Define government surplus?

Surplus, Government:It's a government surplus exists when a government's tax revenues surpasses its total spending (including both program spending and interest charges).

Sustainability: A condition in which economy doesn't utilize more resources from natural environment than can be replenished by normal reproductive capacity of the environment, and doesn't expel more pollution into the environment than can be absorbed without ongoing deterioration in environmental quality. Only a sustainable economy can function long into future without encountering environmental or natural limits.