We use the perfective will have when we are looking back from a point in time when something will have happened.

By the end of the decade scientists will have discovered a cure for influenza.
I will phone at six o’clock. He will have got home by then.

or looking "back" from the present:

Look at the time. The match will have started.
It’s half past five. Dad will have finished work.

We use would have as the past tense form of will have:

I phoned at six o’clock. I knew he would have got home by then.
It was half past five. Dad would have finished work.

We use would have in past conditionals to talk about something that did not happen:

If it had been a little warmer we would have gone for a swim.
He would have been very angry if he had seen you.
 

Exercise

Comments

Hi, all.
Can I say " the house is 3 rooms" instead of "the house has three rooms"?
If I can, is there a difference in meaning ?
What if I have these two options in an exam? Which one should I choose.
Thanks in advance,
Inas

Hello Inas,

'the house has three rooms' is correct and the other form is not. It's certainly intelligible, but native speakers don't speak about houses or rooms that way.

Best wishes,
Kirk
The LearnEnglish Team

hello sir,
Is this statement correct as far as the grammar and the meaning it delivers is concerned?:I would have been having my classes at night if my ticket hadn't gotten confirmed.

Hello magicspeechqwerty,

Yes, that is grammatically correct and it makes sense to me.

Best wishes,
Kirk
The LearnEnglish Team

Hello Kirk or Peter

can i say lie that
or how to finish the sentence

thank you

Hello london16,

Why don't you look up 'lie' in our dictionary – see the search box on the right side of this page – and analyse the example sentences. There you can see how 'lie' is used.

Best wishes,
Kirk
The LearnEnglish Team

Sir, I have a question. Take a situation. Suppose my friend Johnkilled a cat for no reason known to me. So I am just guessing what was in his mind at the time of killing the cat. Here I can say two sentences. Please tell which one of these is correct.

1. John would have thought it was a tiger.
2. John will have thought it was/is a tiger.

Hello Viraj,

'will have' can be used to speak about something in the past that you consider certain. In this case, in which you say you are guessing about John's motivation, I wouldn't use 'will have', as it implies more certainty than a guess. Instead, I'd recommend 'may have' or 'might have'. As far as I know, 'would have' isn't used in the way you use it here.

All the best,
Kirk
The LearnEnglish Team

Thank you sir. So, like if I was more certain in this case for example if I knew that there were a lot of tigers in that place where John was roaming, then could I say that "John will have thought it was a tiger".

Hello Viraj87555,

Not quite. The certainty is not about the tigers, but about John. In other words, you could say 'John will have thought...' if you know John well enough to be sure about his thought processes. You are describing how well you know how John thinks, not whether or not there were tigers.

Best wishes,

Peter

The LearnEnglish Team

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