What is the difference between could have and should have

I'm Seonaid and I hope you like the website. Please contact me if you have any questions or comments. Could have, should have, would have These past modal verbs are all used hypothetically, to talk about things that didn't really happen in the past. See also modals of ability. I could have stayed up late, but I decided to go to bed early. They could have won the race, but they didn't try hard enough. Julie could have bought the book, but she borrowed it from the library instead.

He could have studied harder, but he was too lazy and that's why he failed the exam. I couldn't have arrived any earlier. He couldn't have passed the exam, even if he had studied harder. It's a really, really difficult exam. See also modals of probability. In this case, we don't know if what we're saying is true or not true.

We're just talking about our opinion of what maybe happened. Why is John late? He could have got stuck in traffic. He could have forgotten that we were meeting today. He could have overslept.

He might have forgotten that we were meeting today. He might have overslept. I could have gone directly to college, but I decided to travel for a year. Listen to this song by s teen pop star Tiffany.

The singer is thinking about past possibilities with her lost love. Native speakers often do not pronounce their past tense modals as clearly as Tiffany. I could have been somebody—instead of a bum. To form the negative with these modals, use not between could and have. Could not have means that something was impossible in the past. For example:. She could not have been on that flight because I just saw her at work. It is a way to show strong agreement.

Would have is a bit more difficult because it has two common structures. The first is with but. I would have A, but I had to B. Use this structure to show that you wanted to do something in the past, but you could not. If I had known they were vegetarians , I would have made a salad. You can always reverse conditional sentences. If would have comes first, there is no comma. Past unreal conditionals are very complex; you can learn more about them on a previous episode of Everyday Grammar.

Usually, would have suggests a bad feeling about the past. But not always. In this song by the band Chicago, the singer is surprisingly happy that his ex-girlfriend cheated on him. Her infidelity gave him the opportunity to meet someone else.

And that someone else turned out to be his true love. Should have means that something did not happen, but we wish it had happened. We use should have to talk about past mistakes.

A worried mother might say:. You might remember Lieutenant Dan in the movie Forrest Gump. In the movie, Dan loses both of his legs in the Vietnam War.

He would have died, but Forrest saved him. We all have a destiny. Nothing just happens. I should have died out there with my men.