be certain 的音标为英 [bi ˈsɜːtn]、美 [bi ˈsɜːrtn]，核心含义是“肯定；确信”，表示对某事物有明确把握或判断，语气比 "be sure" 更强调客观依据 。它常通过三种结构表达不同语境：be certain of/about sth 强调对具体事物的确信，be certain to do sth 表示某事“一定会发生”，be certain that+从句 则用于对某个事实或观点的确认 。
be certain of/about sth
后接名词或动名词，指主语对某事物有明确把握。例如：
If you want to be certain of getting a ticket, book now.（要想有把握买到票，现在就得预订）
She is certain of her success in the exam.（她确信自己能通过考试）
be certain to do sth
表示某事“必然会发生”，主语可以是人或物。例如：
He is certain to win the competition.（他肯定会赢得比赛）
The project is certain to be completed by next month.（这项工程下个月肯定能完工）
be certain that+从句
用于对某个事实或观点的确认，从句通常是客观判断。例如：
It is certain that every effect must have a cause.（无疑，每个结果必定有其原因）
I am certain that she will keep her promise.（我确信她会遵守诺言）
be certain of：对……确信；有把握
We are certain of victory.（我们对胜利有把握）
be certain to do sth：一定会做某事
Be certain to notify others about the meeting.（务必通知其他人会议事宜）
for certain：肯定地；确切地
I can't say for certain when he will arrive.（我说不准他什么时候到）
He had to be certain. There could be no room for doubt.（他必须确定无误，不能有任何犹疑）
Be certain to eat slowly and chew your food extremely well.（一定要慢慢吃，细细咀嚼食物）
There will be certain people who'll say "I told you so!"（一定会有人说“我早告诉过你！”）
If they followed the road, they would be certain to reach a village.（如果他们沿着这条路走，一定会抵达一个村庄）
She would break my biscuits in half to be certain I wouldn't choke.（她会把我的饼干掰成两半，确保我不会噎着）