Inflation is defined as a sustained increase in the general level of prices for goods and services. It is measured as an annual percentage increase. As inflation rises, every dollar you own buys a smaller percentage of a good or service. 

The value of a dollar does not stay constant when there is inflation. The value of a dollar is observed in terms of purchasing power, which is the real, tangible goods that money can buy. When inflation goes up, there is a decline in the purchasing power of money. For example, if the inflation rate is 2% annually, then theoretically a $1 pack of gum will cost $1.02 in a year. After inflation, your dollar can't buy the same goods it could beforehand. 

There are several variations on inflation:

• Deflation is when the general level of prices is falling. This is the opposite of inflation.
• Hyperinflation is unusually rapid inflation. In extreme cases, this can lead to the breakdown of a nation's monetary system. One of the most notable examples of hyperinflation occurred in Germany in 1923, when prices rose 2,500% in one month!
• Stagflation is the combination of high unemployment and economic stagnation with inflation. This happened in industrialized countries during the 1970s, when a bad economy was combined with OPEC raising oil prices.

In recent years, most developed countries have attempted to sustain an inflation rate of 2-3%. 

Causes of Inflation 
Economists wake up in the morning hoping for a chance to debate the causes of inflation. There is no one cause that's universally agreed upon, but at least two theories are generally accepted: 

Demand-Pull Inflation - This theory can be summarized as "too much money chasing too few goods". In other words, if demand is growing faster than supply, prices will increase. This usually occurs in growing economies. 

Costs of Inflation 
Almost everyone thinks inflation is evil, but it isn't necessarily so. Inflation affects different people in different ways. It also depends on whether inflation is anticipated or unanticipated. If the inflation rate corresponds to what the majority of people are expecting (anticipated inflation), then we can compensate and the cost isn't high. For example, banks can vary their interest rates and workers can negotiate contracts that include automatic wage hikes as the price level goes up. 

Problems arise when there is unanticipated inflation: 

• Creditors lose and debtors gain if the lender does not anticipate inflation correctly. For those who borrow, this is similar to getting an interest-free loan.
• Uncertainty about what will happen next makes corporations and consumers less likely to spend. This hurts economic output in the long run.
• People living off a fixed-income, such as retirees, see a decline in their purchasing power and, consequently, their standard of living.
• The entire economy must absorb repricing costs ("menu costs") as price lists, labels, menus and more have to be updated.
• If the inflation rate is greater than that of other countries, domestic products become less competitive.

People like to complain about prices going up, but they often ignore the fact that wages should be rising as well. The question shouldn't be whether inflation is rising, but whether it's rising at a quicker pace than your wages. 

Finally, inflation is a sign that an economy is growing. In some situations, little inflation (or even deflation) can be just as bad as high inflation. The lack of inflation may be an indication that the economy is weakening. As you can see, it's not so easy to label inflation as either good or bad - it depends on the overall economy as well as your personal situation.