Currency is represented as an exchange for something valuable, whether it be an object or work.
Prices for objects can change over time, depending on demand and supply, making objects unreliable to measure inflation. Most countries use precious metals to measure or establish currencies, but the prices for metals can also change over time. The amount of work it takes someone to complete a task depends on their physical and mental abilities, in which no two humans are the same.
Is there something that does not change its value that can be used to measure currency inflation?