First, I dont want this to be true but it is.
Currency is a unit.
It is a unit in the system of measurement of value. Just like an inch is a unit in the system of measurement for length.
Units (and there have been thousands of different ones) all have 2 things in common.
1- They are not real. They are all made up, everyone of them is just an opinion. Inch, pound, meter, cat 5, g force,currency --- not real.
the are all just an opinion that we chose to share. We all share the opinion that an inch is so long, if we all shared the opinion that an inch was a foot then it would be.
2- All units are equal to a constant.
This is provablely false. Most units of measurement are, in fact, arbitrarily chosen standards of agreement. Currencies are, truthfully, a unit of measurement; but only of value. Value is, itself, highly subjective. No currency has a constant value relative to anything other than itself, and often not even to itself over time. Yes, Bitcoin is both a currency and a commodity, in many respects; it's also a service, and that service also contributes value to the users.