A sustained increase in the general price level is called inflation.
Inflation means that money’s purchasing power is falling across the economy: a given amount of currency buys fewer goods and services on average. Economists measure it with price indexes such as the Consumer Price Index or the GDP deflator. A single item becoming more expensive is not, by itself, economy-wide inflation.
Inflation can result from strong demand relative to productive capacity, rising production costs, supply disruptions, or changes in money and credit conditions. Moderate inflation can coexist with economic growth, while unexpectedly high inflation can make planning difficult and redistribute wealth between borrowers and lenders.
Deflation is a sustained decline in the general price level. Disinflation means inflation is slowing but prices are still rising. Stagflation combines weak economic performance or high unemployment with inflation. These terms are often confused because they describe different movements in the overall price level or its rate of change.