New words：

certain ['sə:tn] adj. 肯定；确定；确信；无疑
make certain 弄确实；弄清楚；弄明白
for certain 肯定；确定；无疑

Sample Sentences：

We are certain to win the game.
I was certain that he had seen me.
There is no certain cure for this disease.
I can't say for certain when we'll arrive.
Please make certain when the train leaves.

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