Purchasing power stable money
Money with stable purchasing power is idealized money that experiences neither deflation nor inflation . That is, the price level measured in this money remains constant. That does not rule out the possibility of price increases or decreases in some industries , but overall prices remain balanced.
The value of money with stable purchasing power is defined in exactly the same way as a cost of living index or a consumer price index with the special feature that this index, measured in idealized money with stable purchasing power, remains constant over time.