学习资料
[意 思]adj. 不能确信的,不确知
[例]  I am still uncertain whether he will come today. 我仍不能肯定他今天是否会来。
adj. 不明确的,含糊的
[例]  The date of his departure is uncertain. 他离开的日期尚未确定。
adj. 无常的,易变的
[例]  We didn't have the picnic because the weather was uncertain.
我们没有出去野餐,因为天气变幻莫测。