美元dollar是可数名词。复数：dollars
钱，作为一个概念来讲的时候，是不可数的名词。
美元，具体到几块美元的时候，美元就是可数的名词。
相关介绍
Five million dollars has been appropriated for research into the disease.
已拨款五百万元用于这种疾病的研究。
Drugs have been seized with a street value of two million dollars.
黑市价值二百万元的毒品被查获。
It cost somewhere around two thousand dollars.
买下来要花大约两千元。
He gave me five dollars, same as usual.
和平时一样，他给了我五块钱。
