Should have意思

"Should have" is a construction used to indicate that something was not done, although it was expected or necessary. It is used to express regret or criticism about a past action or lack of action. The structure "should have" is formed using the auxiliary verb "should" plus the past participle of the main verb. Here are a few examples:

1. You should have studied harder for the exam. (You didn't study enough, and now you might not pass.)
2. We should have left earlier; we're going to be late. (We didn't leave early enough, and now we're in a hurry.)
3. She should have known better than to trust him. (She trusted him, but she shouldn't have.)
4. They should have called us to let us know they were going to be late. (They didn't call, and we're worried about them.)

The usage of "should have" implies that there was a responsibility or expectation to do something, and that responsibility was not met. It often implies a sense of moral obligation, advice, or recommendation that was not followed.