>>35Inflation is like when we have a balloon and breathe air into it, it still has the same mass (almost) but its volume increases much, so its density decreases. In an analogous way, the density of money, which is value of trade per nominal value, decreases. This is inflation, the decreasing of this ratio.
I guess you are confusing definition and sufficient condition. There are things that can cause inflation other than increases in money supply.