What is the currency of Japan?

The yen, and the name simply means round - adopted in 1871 when Japan replaced a chaotic system of gold, silver and copper coins of varying local value with a single decimal currency modelled on Western practice. The Chinese yuan and Korean won come from the same word for the same reason.

It has no subunit in practice. The sen, a hundredth of a yen, was abolished in 1953 because inflation had made it meaningless, so Japan is one of the few major economies where prices are quoted in whole units only - and where a 10,000 yen note is an ordinary thing to carry, being worth roughly fifty pounds.

Japan is also the most stubbornly cash-based rich country, and the reason is a fair example of infrastructure beating technology. Cash is used because crime is low, ATMs are everywhere including in convenience stores, banknotes are exceptionally hard to forge, and the alternative was never sufficiently better. Contactless payment took hold far faster in countries where carrying cash was riskier or where the banking system was worse.