我觉得这样更能真正理解这几个短语的含义...
sometime表示“将来的某个时候”
Sometimes表示“有时候”
Some time表示“一段时间”
Some times表示“几次”
I will come to see you sometime next week.
下周的某人时候我会来看你.
Sometimes,I play the piano after school.
有时,放学后我弹钢琴.
We will stay here for some time.
我们要在这儿待一段时间.
He called me some times but I wasn't at home.
他给我打了几次电话,但我不在家.