From VOA Learning English, this is Everyday Grammar.

Today we will take a look at the modal verbs could have, would have and should have. These past tense modals are useful for expressing your present feelings about a past decision (or other action).

Could have, would have, and should have are sometimes called "modals of lost opportunities." They work like a grammatical time machine. The simple past just tells what happened. Past modals tell what could have, would have, and should have happened.

To form these past modals, use could, would, or should followed by have, followed by a past participle verb. Use have for all pronouns; never use has or had to form a past modal. Here are some examples:

She could have gone to any college she wanted to.

I would have gone to the party, but I was tired.

He should have told the truth about what he saw.

Each of these modals has a slightly different meaning. We'll look at each of them using examples from movies and popular songs.

Could have

We'll start with could have. Could have means that something was possible in the past, but it did not happen.

I could have gone directly to college, but I decided to travel for a year.

Listen to this song by 1980s teen pop star Tiffany. The singer is thinking about past possibilities with her lost love.

Could have been so beautiful

Could have been so right

Could have been my lover

Every day of my life

Native speakers often do not pronounce their past tense modals as clearly as Tiffany. Could have been usually gets contracted to could've been or even coulda' been.

Listen to Marlon Brando in the classic film "On the Waterfront." Brando's character, Terry Malloy, was once a promising young boxer.

"You don't understand. I coulda' had class. I coulda' been a contender. 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.

Defense lawyers often use could not have to argue for a client's innocence.

A popular compliment in English is, "I couldn't have said it better myself." You can say this when you like the way somebody said something. It is a way to show strong agreement.

Would have

Let's move on to would have.

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.

I would have called, but there was no phone service.

I would have loaned you the money, but I didn't have any.

Would have also forms the result clause of a past unreal conditional. For example:

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.

I would have made a salad if I had known they were vegetarians.

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.

If she would have been faithful

If she could have been true

Then I wouldn'ta been cheated

I would never know real love

I would've missed out on you

Should have

Finally, let's look at should have. 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:

"I was so worried about you. You should have called!"

Should have is common in apologies. For example:

I'm sorry that I'm late for work. I should have woken up earlier.

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.

Listen for should have as Dan confronts Forrest.

"You listen to me. We all have a destiny. Nothing just happens. It's all part of a plan. I should have died out there with my men. But now I'm nothing but a cripple!"

Should have can be used in a light-hearted way. In this song, country singer Toby Keith imagines how exciting his life would be if he had chosen to be a cowboy.

I should've been a cowboy

I should've learned to rope and ride

Wearing my six-shooter

Riding my pony on a cattle drive

I couldn't have said it better myself. As you can see, these modals of lost opportunities offer a colorful way to talk about past choices.

That's all for this week. Join us next week for more Everyday Grammar.

I'm John Russell.

And I'm Dr. Jill Robbins.

Now it's your turn. Leave us example sentence. What is something you could have / should have / would have done in the past?

Adam Brock wrote this article for VOA Learning English. Hai Do was the editor.

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modal verb – n. a verb (such as can, could, shall, should, ought to, will, or would) that is usually used with another verb to express ideas such as possibility, necessity, and permission

contender – n. a person who tries to win something in a game or competition

bum – n. a person who is lazy or who does something badly

compliment – n. a comment that says something good about someone or something

vegetarian – n. a person who does not eat meat

infidelity – n. the act or fact of having a romantic or sexual relationship with someone other than your husband, wife, or partner

confront – v. to oppose someone, especially in a direct and forceful way

cripple – n. a person who cannot move or walk normally because of a permanent injury or other physical problem

six-shooter – n. a kind of gun (called a revolver) that can hold six bullets (often used to describe guns used in the old American West)

cattle drive – n. the process of moving cows from one place to another