Bitcoin was never a currency, most of people use bitcoin as an alternate and anonymous payment method without higher transaction fees while others used bitcoin as an investment.A currency is backed by bank or solid collateral but with bitcoin there is nothing like this.
Alternate currency, it's the right name for bitcoin at this time but it will grow become the main currency(digital). I can't call it a currency because based on bitcoin is not have a physical form. But every time the definition of the currency always changes.