currency是不可数名词。译为：通货;货币;通用;流行;流传
复数： currencies
Tourism is the countrys biggest foreign currency earner.
旅游业是这个国家赚取外汇最多的行业。
Supply and demand on the currency market will generally balance.
货币市场上的供求将大致持平
It is customary for people in US to slang, but many slang words have short currency.
美国人习惯用俚语，但很多俚语词汇流行的时间很短。
The meaning of hard currency is here.
硬通货的意思就在这里。
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