1 (not before a noun 不用于名词前) certain (that...);certain (of sth) completely sure; without any doubts 确信；肯定；确定: She's absolutely certain that there was somebody outside her window. 她确信窗外有人。We're not quite certain what time the train leaves. 火车什么时候开，我们不大有把握。I'm certain of one thing -- he didn't take the money. 有一点我是肯定的，他没拿那个钱。

2 certain (that...);certain (to do sth) sure to happen or to do sth; definite 必然的: It is almost certain that unemployment will increase this year. 今年的失业人数会上升，这差不多成了定局。The Director is certain to agree. 主任一定会同意。We must rescue them today, or they will face certain death. 今天我们必须营救他们，要不他们必死无疑。

3 (only before a noun 只用于名词前) used for talking about a particular thing or person without naming him/her/it 某；某些: You can only contact me at certain times of the day. 一天里你只有某些时候可以跟我联络上。There are certain reasons why I'd prefer not to meet him again. 为了某些原因我不想再跟他见面。

4 (only before a noun 只用于名词前) some, but not very much 一些；不多: I suppose I have a certain amount of respect for Mr Law. 我想我对劳先生怀有一点敬意。

5 noticeable but difficult to describe 一点的；稍微的: There was a certain feeling of autumn in the air. 那时候已略有秋意。

6 (formal 正式) used before a person's name to show that you do not know him/her （置于人名之前表示跟此人不相识）: I received a letter from a certain Mrs Berry. 我收到一位贝里太太的来信。

1 to do sth in order to be sure that sth else happens 确保: They're doing everything they can to make certain that they win. 他们正在尽一切努力确保胜利。

2 to do sth in order to be sure that sth is true 弄清楚: We'd better phone Akram before we go to make certain he's expecting us. 我们离开前最好打个电话给阿克拉姆，以确定他在等我们。