As noted elsewhere by a prominent author in the area [25], there is not a widely accepted or consistent definition of the term “bubble”. The GDASF test used here assumes a bubble is any time series interval which deviates from a random walk to become explosive.
CYNTHIA LUMMIS: My son-in-law has a shirt that says friends don't let friends sell bitcoin. And that is my investment strategy for bitcoin.

“Everybody’s definition of a headquarters of a company is different. When you ask how you define a headquarters --- is that an office where people sit? I worked from home for the last three and a half years. Our leadership team are not sitting in one office, we don’t have a clear place where we can go, by most people’s normal definitions of a headquarters that we can call a headquarters. So, when people ask me, I don’t want to give them a wrong answer just to satisfy their definition.”
Each asset holds a value, often priced in U.S. dollars, which leads to another use case: trading and investing. Aside from stablecoins — which seek to stabilize the instability of cryptocurrencies by pegging an asset to something else, such as the U.S. dollar — most cryptocurrencies constantly fluctuate in price. You can trade between cryptocurrencies and national currencies (called fiat currencies) on exchanges, depending on the trading pairs available on the platform of choice.