美元是可數名詞還是不可數名詞?

　　The dollar finished the day slightly down.

　　當日結束時美元匯率略有下降。

　　What's the rate of exchange against the dollar?

　　與美元的兌換率是多少？

　　Here's a five dollar bill ─ please keep the change.

　　這是一張五元的鈔票——零錢就不用找了。

　　If you want the best, you have to pay top dollar.

　　你想要最好的，就得花大錢。

　　The US dollar went through a difficult time, in company with the oil market.

　　美元與石油市場同時經歷了艱難時期。