Medium of exchange
Bitcoin acts as a medium of exchange when parties settle an obligation with it. An on-chain payment offers globally verifiable settlement; Lightning supports faster small payments with different channel, liquidity and backup requirements.
Practicality depends on merchant acceptance, fees, confirmation needs, exchange-rate movement, interface and local rules. A processor can convert BTC immediately into euros, so the customer pays bitcoin while the merchant holds no bitcoin balance.
Unit of account
A unit of account is the scale used for prices, wages, contracts and books. If a shop lists EUR 20 and converts it into satoshis at checkout, the euro remains the economic unit of account.
Genuine BTC pricing leaves an obligation at, say, 100,000 satoshis when the exchange rate changes. Volatility and tax or accounting rules can make that difficult. A small community may adopt it before a whole economy does.
Storage and exchange can diverge
One person may hold bitcoin for years and never pay with it; another may buy just before a transfer while the recipient sells immediately. Both use the network but create different demand and risk.
Expected appreciation may encourage holding rather than payment, but this is not a mechanical law. People spend appreciating assets when the benefit of a purchase exceeds the benefit of holding. Preferences and alternatives decide.
- a medium of exchange settles an obligation
- a unit of account quotes prices
- a store of value carries purchasing power through time
The conclusion depends on place and period
Academic work on older data found predominantly speculative holding and weak performance of traditional currency functions. Infrastructure has changed since, but that historical result cannot simply be inverted into a claim that Bitcoin is now everyday money everywhere.
State the context: who, where, on which layer and in what unit sets prices. Bitcoin is a functioning payment and settlement system; the breadth of daily medium-of-exchange and unit-of-account use is an empirical question, not a protocol definition.