The Yuan is the basic unit of Chinese currency, the Renminbi. Even if renminbi is the official name of the currency, Chinese Yuan is the name of the currency that is internationally used.
The word yuan translates to "round object". this is because in Qing dynasty the yuan was a round silver coin.
The term yuan is used both as the singular and the plural for the currency.
The correct pronunciation of Yuan is You-wuhn.
Yuan is often pronounced mistankely as you-win or you-wen. The difficulty of pronouncing Yuan correctly is that the "a" does not have a specific correspondent in the English language. Because of this, even the transcription of Yuan as You-wuhn is close but not perfect. The "a" in Yuan is pronounced with a sound that is midway between an "e" and an "a" sound, which closely approximates to a "uh".