exercise的复数是什么时候用，希望能讲清楚并举例

1，exercises通常用于表示练习题如：
My teacher often tells us to do more math exercises every day.
2，用于表示体操、保健操。
Doing morning exercises is good for our health.

作 习题 或者前面加了形容词构成特殊词(例如morning exercises）时可用