Is PPP a theory of exchange rate determination in the long run or in the short run?

Question:

Is PPP a theory of exchange rate determination in the long run or in the short run? Briefly explain.

Exchange Rate
The value of one currency for the purpose of conversion to another. Exchange Rate means on any day, for purposes of determining the Dollar Equivalent of any currency other than Dollars, the rate at which such currency may be exchanged into Dollars...