Revaluation means a change of a price of goods or products. This term is specially used as revaluation of a currency, where it means a rise of currency to the relation with a foreign currency in a fixed exchange rate. In floating exchange rate correct term would be appreciation.
Devaluation in modern monetary policy is a reduction in the value of a currency with respect to those goods, services or other monetary
units with which that
currency
can
be exchanged. It means official lowering of the value of a currency within a fixed exchange rate system, by which the monetary authority formally sets
a new fixed rate with respect to a foreign currency.