a.

1. 确信的，有把握的[Z][F][+（that）][+wh-][（+about/of）]
   I'm not sure whether our team will win.

   我不能肯定我队是否能赢。

   We are sure of his innocence.

   我们确信他是无辜的。

2. 一定的，必定的[Z][F][+to-v]
   She is sure to write to you.

   她一定会给你写信的。

3. 确实的；可靠的
   One thing is sure, he won't let you down.

   有一点是确定的，那就是他不会让你失望。

   Exercise is a sure way of losing weight.

   运动是减肥的可靠办法。

4. 稳健的；稳固的

ad.

1. 【美】【口】的确；一定；当然
   It's sure cold outside.

   外面实在很冷。

adj.

1. completely confident that one is right.
2. (sure of/to do something) certain to receive, get, or do something.
3. undoubtedly true; completely reliable.
4. confident or assured.

adv.