A useful thing as the subject of barter.
Bitcoin is a constructive possession. An ability to possess and direct. Bit coins are a property. Not a security or a contract.
It is a commodity like gold.
It must be recorded as bayses in and returns out, for tax period.
As for trademark, No patient, the name is so use it outside any copyright as fair use. That is to say the name is in wide piblick use and cannot be traced to its creator or owner.
A Privet Key assigns an address to the hash. The address being the Publicly Key and the hash being the Bitcoin.
to the hash (the hash is a string of numbers created by applying the nonce,created from the meem.) to a known number in