Currency Indices The value of a country's currency against another country's currency is called parity. Likewise, when expressing the value of one currency, we say its value against another currency. The first currency in a parity pair is called the Base Currency. For example; In USDTRY parity, the base currency is the US Dollar. The second, variable currency unit of the pair is called the Counter Currency. For example; In USDTRY parity, the counter currency is the Turkish Lira. ** If we say that there has been an increase in the USD / TRY parity, we mean that the dollar has risen or the TL has depreciated.