How is money’s loss of value measured?

When a country’s money supply grows very rapidly, money inevitably loses value. But the question is how to measure money’s loss of value: relative to what? There are three possibilities: The country’s currency loses value relative to the currencies of other countries, i.e. the exchange rate depreciates; Money loses value in terms of its ability to buy goods and services, i.e. the prices of goods and services rise; Money loses value in terms of its ability to buy assets (equities, real estate, speculative assets, etc.), i.e. asset prices rise. In contemporary OECD economies, it is this third form of loss in value of money that is systematically observed. The first (exchange rate depreciation) can be observed in the euro zone and Japan, but not in the United States. The second (inflation) cannot be observed anywhere.