The term nonrenewable resource refers to a natural substance that is not replenished with the speed at which it is consumed. As such, a nonrenewable resource is a finite resource. Humans constantly draw on the reserves of these substances while the formation of new supplies takes eons. Examples of nonrenewable resources include fossil fuels like oil, natural gas, and coal. The opposite of a nonrenewable resource is a renewable resource. The supplies of these resources replenish naturally or can be sustained.