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.