for a certainty/for certain
for sure；without doubt确定地；无疑地
Iknow it for a certainty that he'll get a promotion．我的确知道他将被提升。
I know for a certainty that he came from Shanghai．我确实知道他来自上海。
He left town a week ago， I know this for a certainty．他一星期前离开了这个城市，这一点我确实知道。
Do you know it for certain？你对这件事肯定知道吗？
I could not say for certain that he was wrong．我不能断然地说他错了。
I know for certain that he has come．我确实知道他来了。