To date, this has largely defined what money is… those two properties together, although I would state it a bit differently.
Traditional currency has two key properties:
unit of measure
what everything else is measured in terms of
the key desirable property is it has to be less volatile than other assets, which people talk about as being a “store of value”
it is not seasonal
doesn’t change much with the business cycle
stable-ish over long periods of time so you can arrange payments than span decades
unit of exchange
The other key aspect of money is that it has to be easy to use
key properties: transportable, storable, fungible, easy to tax
but really, currency is just “I will pay you X value worth of Y asset”
I will pay you $1 worth of Ada
I will pay you $1 worth of USD
anyway, with the whole digital money - most people are already more than happy to take a lot of things worth a dollar instead of a dollar: a credit card, a gift certificate, a traveler’s check (if you remember what those were), or any asset you can trivially turn into a dollar is basically the same as a dollar to me.
With digital assets: basically everything is equally easy to transfer or hold, so I am pretty skeptical about ideas of artificial scarcity - we will only accept “X” instead of something “worth X that is trivially converted into X”. If I am running a store, I will gladly accept anything you want to pay me with - as long as it’s easily exchangeable for what I want.
Pay you in BTC? sure, I’ll can do that - but the price will be in USD. or GBP. or something more stable. No way I want to commit to a price in an asset that can 10x.
that unit of measurement is really what defines a modern currency, because most digital assets are all equally easy to exchange.