Even if so called "price inflation" is the most common usage it's still a meaningless misuse invented by Keynsians who wanted to obfuscate the meaning of the word and distract us peasants from recognizing the true culprits of inflation who are obviously the people controlling the money supply.  Since prices are different and vary differently for every different good and goods themselves change over time there can be no "price inflation" generally speaking.  There is no metric to possibly compute it from the myriad of individual prices that exist in the economy.  Any metric such as CPI, PPI, etc is completely arbitrary and anyone can come up with any value they'd like since there's no particular computation that's any better than any another.  Prices are what they are and they can rise and they can fall for a particular commodity.  It's completely disingenuous to introduce a word that has a precise meaning in a totally meaningless context that's only meant to destroy the original meaning and cause confusion.