Yuan is used as money, such as in America how we use dollars or how Mexico uses pesos or how the UK uses pounds
A yuan (Chinese: 元; pinyin: yuán) is also known colloquially as a kuai (Chinese: 块; pinyin: kuài; literally: "lump"; originally a lump of silver). One yuan is divided into 10 jiao (Chinese: 角; pinyin: jiǎo; literally: "corner") or colloquially mao (Chinese: 毛; pinyin: máo "feather"). One jiao is divided into 10 fen (Chinese: 分; pinyin: fēn; literally: "small portion").
It is English if you expect Chinese people to call our currency unit "dollar". We correctly call their currency unit "yuan".