High inflation has appeared in the last two years in Greece and the international economy, after a long absence. Our country has a heavy history: it experienced 22 years with double-digit inflation, 17 with single-digit, 9 with zero or "negative." We have inflation when prices rise, and this brings about high costs. However, it is different when something "becomes expensive," another when something "is expensive," and another when there is "high cost." Inflation is a flow of prices, which is why it is usually measured as a percentage increase. High cost is measured against the level of income. For economists, inflation is a monetary phenomenon and refers to the value of money. For consumers and entrepreneurs, inflation is a disease of the currency. But how do we measure inflation, how and when do we hope the battle will be won, and with what tools? The series SMALL INTRODUCTIONS includes reference books, written by experts, which provide valid and in-depth information on topics of immediate interest. Simple but not simplistic, scientific but not inaccessible, short but complete, the series offers the modern reader the keys to deeply understand our complex and changing world.