sometime表示百分之几
sometimes表示百分之三十。
She comes to visit us sometimes.    她有时来访问我们。
I sometimes think that it is a great mistake.    我有时想这是一个大错。
It is sometimes warm and sometimescold.    天时热时冷。
Sometimes I will go to the university for the elderly.
有时我会去上老年大学。