250 may be written using either Arabic numerals (250) or Chinese
numerals (二百五å) in Japanese. However, both are pronounced
as "ni-hyaku-go-juu".
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No, Japanese numbers work like Arabic numbers. There is a
match.
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The word itself for numeral(s) is æ•°å—(suuji) in Japanese. See the related question below if you're interesting in counting in Japanese.
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The number 20 is commonly just written using Arabic numerals (20) in Japanese, but the Chinese numerals may also be used (二十). Both ways are pronounced as 'nijuu' (rough pronunciation: "knee-jew").