例句：For certain reasons I will be unable to attend the meeting.
因为某种原因，我不能出席这次会议。
certainly adv. 的确，(口语)当然，行
例句：You certainly did well today.
你今天做得不错。
certainty n. 确定，确实的事情
例句：I can’t say with certainty what project they arc engaged in.
我无法肯定他们在进行什么项目。
ascertain vt. 确定，探知
例句：My purpose is to ascertain whether you are interested or not.
我的目的是要确定你是否感兴趣。
uncertain adj. 无常的，不确定的，不可预测的，靠不住的
例句：I am still uncertain whether Henry will come today.
我仍不能肯定亨利今天是否会来。
