“Must” / “can’t”

   

 
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General English
Grammar

Welcome to your “Must” / “Can’t” lesson! In this topic we talk about:
• “Must” and “Can’t” in the present
“Must” and “Can’t” in the past
Take the quizzes when you’re ready! If you’re having problems, use the comment box to contact our English Teachers.

“Must” and “Can’t” in the present

“Must” is used when you believe something is certain:

“You live in the mountains? It must be cold up there.”

“She’s been walking all day, she must be tired.”

“You think that English breakfast is disgusting? You must be joking.”

“Can’t” is used when you believe something is not possible:

“You’ve had twelve hours sleep, you can’t still be tired!”

“That restaurant is empty, it can’t be very good.”

I / You / We etc.

must

can’t

be (joking / going / doing etc.)

be (tired / hungry / sad etc.)

do / know / say etc.

“Must” and “Can’t” in the past

For the past, we use “must have” and “can’t have”:

“She didn’t answer her phone, she must have been asleep.”

“Where are my keys? I must have dropped them.”

“He didn’t come to the party, he can’t have got the invitation.”

“They burnt the eggs, they can’t have been concentrating.”

I / You / We etc.

must

can’t

have

been (joking / doing / going etc.)

been (tired / hungry / sad etc.)

done / known / said etc.

“Can’t have” can be replaced by “couldn’t have”:

“He didn’t come to the party, he couldn’t have got the invitation.”

“They burnt the eggs, they couldn’t have been concentrating.”

Recap

  • “Must” is used when you believe something is certain.
  • “Can’t” is used when you believe something is not possible.
  • For the past, we use “must have” and “can’t have”.
  • “Can’t have” can be replaced by “couldn’t have”.