Bitcoin is not really a currency. It's even more volatile that most FIAT currencies.
It is a currency and it's only volatile when you peg it to other currencies.
No, it is also volatile when measured as the cost to buy things, for almost all merchants.
Yes, it's not just when pegging it "to other currencies" but to
purchasing power. That's what is important here. In that light, the dollar is relatively stable. Bitcoin is extremely volatile.