Successful currencies meet three criteria:
(1) they are in widespread use as medium of exchange
(2) they serve as unit of account
(3) they are a stable store of value.
Most sovereign currencies fully meet all three criteria.
What about Bitcoin?
Many people still refused to understand that bitcoin is a currency duo we all know that it not yet legalized just like other local currency to it still place great row in the aspect of online payment, many online trade can now use bitcoin to purchased or pay of service online using bitcoin so with this it already absolving the row of currency.