We have here not only a problem in economics, but in semantics.
Inflation used to mean an increase in the money supply disproportionate to the growth of goods and services. The result of this circumstance is rising prices. Under this definition and ones like it, inflation is a cause of rising prices, although not the only one.
Then journalists and a lot of other people who should have been more careful with their language started to use the word “inflation” as a synonym for increasing prices, even though there are other circumstances besides inflation of the money supply which can cause price of one thing or another to increase. These other causes include price fixing by suppliers and increased demand because of new uses for a commodity, and increased demand because of speculative investment, and increased demand simply because of a rumor, or a fad.
Back in the 70s newspapers and magazines started saying things like “Rising Prices Fuel Inflation”, which is sort of like saying “accidental fires lead to spilled gasoline”. Or at least it was like saying that. At first a lot of people complained about this kind of sloppy language but in time the concept of rising prices and inflation became so conflated that the term “inflation”, in common use, and even in many discussions by economists, has effectively no clear, distinct meaning any more.
This has resulted in making inflation of the money supply harder to discuss sensibly and to deal with. This is particularly unfortunate as economics tends to deal with abstractions which are hard to picture precisely anyway.
Take, for instance, the whole idea of “the money supply”. Currency is not the same thing as money. Money is an abstraction (although a very real one), and “the money supply” is an intangible which is represented in part by currency but far more by entries in bank ledgers; as noted above, the level of borrowing is the single most significant factor in determining the size of the money supply.
Why is money worth anything? Because it can be used to buy things.
Suppose there were an economy on an island somewhere in which there were just two things to trade in, say, pineapples and clams. Suppose further that the supply of these was about equal, and people valued the two things about equally. It is easy to picture that one pineapple would be worth about one clam, and vice-versa. Suppose further that one day clams suddenly become far more common, so that the island is postively inundated with them.
Everybody now has a lot more clams. So: is everybody rich? Not if everything else on the island remains the same; a person can only eat so many clams, and there isn’t anything else that can be done with them except trade them for pineapples. It is fairly easy to picture that the individual clam is now worth less than before, and the individual pineapple (as measured in clams) is more valuable.
For “clams” substitute “money” and for “pineapples” substitute “goods and services”.
When the supply of money is increasing faster than the supply of things that can be bought with it, indivdual units of money lose some of their value relative to the stuff they can buy; the increase in the supply of money does not represent an increase in real substance or value; it is just so much hot air; it’s just so much…“inflation”.