BTC are divisible to 8 powers of ten. That is the smallest fraction of a BTC would be 0.00000001. Maybe this will be called fractional currency expansion?
And the dollar has a fraction of 0.01, many internal accounting systems have many more digits after the coma, where's your point?
If your point is, that BTC is supposed to increase in value to the point (in a distant future) where we will be paying with mBTC or uBTC, there's a term for that, it's called deflation. So what was your point again?
Ahh, no. It's not. That would be currency appreciation, not deflation. I don't understand why this concept is so hard. From an economic perspective, deflation is a (relative) reduction in the monetary base in circulation. Changes in the value of the currency/the prices of goods in that currency is often a
symptom of deflation or inflation, but changes in the monetary base are not the only (or even the majority) reason for such visable symptoms.