Modals: deductions about the present

Modals: deductions about the present

Do you know how to use modal verbs to say how certain you are about a possibility? Test what you know with interactive exercises and read the explanation to help you.

Look at these examples to see how must, might, may, could and can't can be used.

That must be the main entrance. I can see people queuing to get in.
I've lost my keys. They might be at work or they could be in the car.
You can't be bored already! You've only been here five minutes. 

Try this exercise to test your grammar.

Grammar test 1

Modals – deduction (present): Grammar test 1

Read the explanation to learn more.

Grammar explanation

We can use modal verbs for deduction – guessing if something is true using the available information. The modal verb we choose shows how certain we are about the possibility. This page focuses on making deductions about the present or future. 


We use must when we feel sure that something is true or it's the only realistic possibility.

This must be her house. I can see her car in the garage.
He must live near here because he always walks to work.
Come inside and get warm. You must be freezing out there!

might, may, could

We use might, may or could to say that we think something is possible but we're not sure. 

She's not here yet. She might be stuck in traffic.
He's not answering. He could be in class.
We regret to inform you that some services may be delayed due to the bad weather.

They all have the same meaning, but may is more formal than might and could.


We use can't when we feel sure that something is not possible.

It can't be far now. We've been driving for hours.
She can't know about the complaint. She's promoted him to team leader.
It can't be easy for him, looking after three kids on his own.

Note that these verbs, like all modal verbs, are followed by an infinitive without to.

Do this exercise to test your grammar again.

Grammar test 2

Modals – deduction (present): Grammar test 2

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Submitted by ShetuYogme on Tue, 14/05/2024 - 09:21


Hon'ble LearnEnglish Team,

In this article, we studied modal verbs used for "deduction about the present": must, may, might, could etc.

I have learned somewhere that the modal verb "will" can also express beliefs about the present. For example: 
1. Sam will be at home. (This is a belief about the present) 
2. Don't phone my friend. He will be sleeping now. (This is again a deduction about the present)

If "will" can be used to express deduction about the present, what is the difference between "will", and "must" and "may/might/could"? Could you please explain in detail giving several examples and references?

I have also seen some people use "would" to express deduction about the present. For example: 
1. That old man would be 80 full stop 
2. He would be at home. 
Is it correct to use "would" in the sense it has been used in these two sentences?

Could you please help me understand these nuances with explanations, examples, and references, if any?

Hi ShetuYogme,

"Will" expresses either certainty or a prediction. For example, in Sam will be at home, the speaker is either certain that this is true, or believes or guesses that it is true.

That is a bit different from deduction, because a deduction is a logical process and it is always based on some kind of evidence or reasoning (while a guess or a belief is not). For example, if I say Sam must be at home, it implies that I am stating this for some reason (e.g. because I know that Sam is always at home at this time every day). "Must" emphasises the logic and reason that resulted in making this statement. "Will" does not, and it simply emphasises that I am certain about it or that I believe this to be true.

"Might" and "could" express only a moderate level of confidence that the statement is actually true.

"Would" expresses similar meanings to "will", but with somewhat less confidence.

I hope that helps.


LearnEnglish team

Hi again,

When you say "will" express certainty, does "Sam will be at home" mean "Sam is at home"? 

Can "you will have enjoyed the party" mean "you enjoyed the party"? Is it possible to use "will have" to refer to past certainty and predictions? 
Does "you would have enjoyed the party" mean "you enjoyed the party", the speaker saying with less confidence and it is not a conditional sentence?

Thank you.

Hi ShetuYogme,

They are similar, but there are nuances. "Sam will be at home" includes the meaning of "I believe this to be true". It does not mean simply "Sam is at home", but is closer to "I believe that Sam is at home". 

In comparison, "Sam is at home" (present simple) is a factual statement. The issue of what the speaker believes is irrelevant to this statement, since it is presented as a fact.

Yes, you can use "will have" for past certainty and predictions. "Will have" and past simple have the same difference in meaning as the difference between "will" and present simple, described above.

About "you would have enjoyed the party", this particular sentence and context seem more likely to mean an unreal and imagined past action, i.e. the person did not in fact go to the party. This is a conditional meaning: "You would have enjoyed the party, if you had gone to it".


LearnEnglish team

Hi again, 

I still have confusion about will, would and must. You told He will be at home mean I think he is at home. He would be at home means the same but with less confidence. You told that would have for the past can not be used in this way but will have can be. Why so?

I have seen people using Sonam would have enjoyed the movie to mean They think or believe that Sonam enjoyed the movie. This seems to be similar to Sonam must/might have enjoyed the movie.

But Sonam will have enjoyed the movie s  seems to be an example of future perfect. 

I'm too confused. Could you please help me do away with my confusion.

Thank you for your help.

Hi ShetuYogme,

I'll try my best to clarify!

Actually, in my previous comment, I wrote: "About "you would have enjoyed the party", this particular sentence and context seem more likely to mean an unreal and imagined past action"

My comment was about the use of "would have" in this particular sentence, not about "would have" in general. It also does not say that "would have" cannot be used for a past certainty/prediction, but that instead it would be more common (in my view) for somebody to say this sentence with the conditional meaning. As you can see, I am commenting about real life usage, not just about what is grammatically possible or not. 

For He would be at home and Sonam would have enjoyed the movie, I can imagine situations where people would actually say these sentences with the past certainty/probability meaning. But for You would have enjoyed the party, I find it less obvious. I could say that sentence about Sonam because presumably Sonam is not present, so I must predict his views on the movie. But in what actual situation would you tell somebody directly You would have enjoyed the party directly? Why would you not feel so confident about it? Why would you not say something more conversational (e.g. "Did you enjoy the party?")? Again, I'm not saying that it's impossible to say You would have enjoyed the party with the past certainty/probability meaning. I just find it less a likely thing to actually say.

Meaning comes not only from grammar, but from words and context, so you shouldn't think that simply understanding "would have means X" enables you to understand every example of the use of "would have". Since "would have" has various meanings, readers/listeners need to use contextual information (e.g., other things that are said in the rest of the conversation; knowledge of other similar situations) to work out which meaning of "would have" is presently relevant. So, you're right that the Sonam example could be an example of future perfect, instead of a past certainty/probability. But since here we only see the words, and we don't know the context of saying those words, nobody can know for sure which exact meaning is intended. We can only make a guess about the likely meaning, based on our knowledge of other similar situations.

Sorry for the long answer, but I hope at least it explains my previous one!


LearnEnglish team


I also have the same views. From my knowledge of conditional sentences, the sentence You would have enjoyed the party is more likely an example of a third conditional. The complete sentence could be: If you had attended the party, you would have enjoyed the party. But I have seen so many people using this sentence not in a conditional sense but about what they think has happened in the past and past certainty. For example, I went to a party of my friends yesterday. My brother didn't go to the party. I came back to my home at night. Now my brother thinks that I enjoyed the party that took place yesterday. So he said to me, "You would have enjoyed the party."

But I have seen no one saying You will have enjoyed the party.

I thank you for the response you gave me clarifying my doubts.



Submitted by DoraX on Mon, 09/10/2023 - 09:11


Hello again LearnEnglish Team,
I'd like to ask you something more about "must" and "have to". Are both of them used to give advice as in the following sentences "You must take a rest" and "You simply have to get a new job." ? If yes, what's their difference?

Hello DoraX,

In general, we use 'should' to give advice and 'must' or 'have to' more to express obligation.

This doesn't mean that it's never appropriate to use 'must' or 'have to' to give advice, but I'd recommend you be very careful about using them. For example, imagine I say 'You have to see the film!' to a close friend of mine. In the context of our friendship and the conversation we're having, and especially when delivered with an appropriate tone of voice, I can be reasonably sure that he will understand that I'm not actually ordering him to see the film, but rather am suggesting it.

But it could be a real mistake to say the same thing to my boss or to a person I don't know well. They could even feel offended if they misunderstood my intentions. For this reason, it's generally better to use 'should' (which is also appropriate with your close friends).

Does that make sense?

All the best,
LearnEnglish team