you are not investing in something
That's, pedantically, true. If don't create capital with it, "investing into Bitcoin" may sound grammatically incorrect. Neither do you, though, when you use a fiat currency. Don't mess investments with currencies, let's take it one at a time.
Since I've seen you're keen on definitions, let's see how Wikipedia defines what's "currency":
A currency[a] in the most specific sense is money in any form when in use or circulation as a medium of exchange, especially circulating banknotes and coins.[1][2] A more general definition is that a currency is a system of money (monetary units) in common use, especially for people in a nation.[3] Under this definition, U.S. dollars (US$), euros (€), Indian rupee (₹), Japanese yen (¥), and pounds sterling (£) are examples of currencies.
So, a currency is, by definition, used as intermediary to exchanging. A country may create its own to handle the economy. It, therefore, legalizes its use. People use the currency, because they live inside the country. The administration of it happens from the central bank of the country.
Is everything good so far?
Sure, a currency is money in some form. That's true. A key word is "some". So something has to exist to be a currency. Some commodity, debt, equity, good, whatever. That's why I am asking where is cryptocurrency called bitcoin? I see math symbols attached to address. But I see nothing else. That's why I am asking you. And you are keep talking about irrelevant things. Or giving definitions of existing things. If you say that bitcoin is a digital currency, a digital product, you have to be able to show it. If I say that I have a specific quantity of digital products, such as pictures, sounds, videos or applications, I am able to show these products to you. But all you can show me is mathematical symbols attached to addresses. They are supposed to inform us about the specific quantity of a digital product called bitcoin. But where's bitcoin? How do you know bitcoin is digital if you're not able to show it?
Anyone can write a computer program that will attach math symbols to addresses and then claim these symbols quantity a particular product. But the key question is: where is that product? What is it? That's why I've asked the question: what is bitcoin? But all of you here are ignoring the question. You, for example, keep talking about bitcoin, but all that exists are math symbols. The owner of an address with this symbol: "0" supposedly owns zero bitcoins. Someone with this symbol: "1", supposedly owns one bitcoin. And someone with this symbol: "8", supposedly owns eight times more bitcoins than the previous owner. Eight times more of this digital product. And it is said this product is revolutionary. But where's this revolutionary digital product? How do you know it's revolutionary if you're not able to show it?
So, can you tell me where is this product located? Blockchain only has addresses and math symbols attached to them. All three address owners mentioned above, have equal number of symbols. Only the shape of symbols is different - "0", "1", "8". But the last owner supposedly has eight times more of this bitcoin than the previous owner. So, can you tell me where bitcoin is located?