The modal verbs are can, could, may, might, mustshall, should, will and would.

The modals are used to show that we believe something is certain, probable or possible:


We use the modals could, might and may to show that something is possible in the future, but not certain:

They might come later. (= Perhaps/Maybe they will come later.)
They may come by car. (= Perhaps/Maybe they will come by car.)
If we don’t hurry we could be late. (= Perhaps/Maybe we will be late)

We use could have, might have and may have to show that something was possible now or at some time in the past:

It’s ten o’clock. They might have arrived now.
They could have arrived hours ago.

We use the modal can to make general statements about what is possible:

It can be very cold in winter. (= It is sometimes very cold in winter)
You can easily lose your way in the dark. (= People often lose their way in the dark)

We use the modal could as the past tense of can:

It could be very cold in winter. (= Sometimes it was very cold in winter.)
You could lose your way in the dark. (= People often lost their way in the dark)


We use the negative can’t or cannot to show that something is impossible:

That can’t be true.
You cannot be serious.

We use couldn’t/could not to talk about the past:

We knew it could not be true.
He was obviously joking. He could not be serious.


We use the modal must to show we are sure something to be true and we have reasons for our belief:

It’s getting dark. It must be quite late.
You haven’t eaten all day. You must be hungry.

We use must have for the past:

They hadn’t eaten all day. They must have been hungry.
You look happy. You must have heard the good news.

We use the modal should to suggest that something is true or will be true in the future, and to show you have reasons for your suggestion:

Ask Miranda. She should know.
It's nearly six o'clock. They should arrive soon.

We use should have to talk about the past:

It's nearly eleven o'clock. They should have arrived by now.




Khuder, I'm from Brazil and I'm not 100% sure about what I'll tell you now, but, in my opinion, you need to learn how to use only the modal "Could", as soon as you learn it, you will be able to use it with "have" cause it will sound clearer for you. In your example "They could have arrived", it might be more difficult if you analyse it out of a context for example. Oh, they could have arrived many hours ago, lets prepare something to them... So in this case they "maybe yes/not have arrived many hours ago, it's a possibility but you prefer to prepare something to them...
They could have killed him... Is not 100% of sure that they killed him, maybe yes maybe not, it will rely on an investigation...
I don't know if I helped you but I tried.
Bye bye.

Hello khuder,

Modals have lots of different uses, so it's best to take them in small doses! 'could have' implies that the possibility existed but was not realised, so, for example, in your two examples, they did not arrive hours ago and they did not kill him. If you want to make it clear that something was possible and did happen, most of the time you'd probably just use a past simple form, e.g. 'they arrived hours ago', 'they killed him'.

All the best,
The LearnEnglish Team

Hi there,
I'm always baffled by the 'would'. how to differentiate that would in the sentence is conditional or talking about the possibility ( like might or could )?. Do we need to consider the whole context to differentiate between these two? for instance, this paragraph is talking about the Computer Networking terminology.

" Data link layer protocols add a trailer to the end of each frame. The trailer is used to determine if the frame arrived without error. This process is called error detection and is accomplished by placing a logical or mathematical summary of the bits that comprise the frame in the trailer.

Error detection is added at the data link layer because the signals on the media could be subject to interference, distortion, or loss that would substantially change the bit values that those signals represent."

It would be great if you could help me on this regard.


Namaste Kiran,

'would' and all of the different modal verbs can indeed be difficult to learn to use, as they all have multiple uses is different contexts. 'would' is not used to talk about possibilities in the same way as 'may' and 'might'; rather, it communicates the idea of something unreal (e.g. because it's hypothetical or imaginary).

We don't normally comment on texts from other sources, but I'll try to help you with this one since it's very specific. In the fourth sentence, the 'because' clause is talking about a hypothetical situation, more specifically a situation in which the signal is subject to interference. Since this signal interference situation is hypothetical, the changes in the bit values that would result because of it are also hypothetical. The hypothetical nature of this signaled by 'would'. If we said 'will', it implies more reality than is appropriate for this situation.

Does that help?

All the best,
The LearnEnglish Team

Hi Kirk
Thank you very much for spending your time to answer my query and providing this valuable lesson.
Sorry to bother you again but
I'm always confused with this two conversation:

1. 'Would' as a possibility. For example, David is not sure who is knocking on the door and says 'That would be Sam'.

2.Sam says to his Australian friend about Bondi Beach in Sydney 'American would pronounce Bondi ('i' like miss) instead of Bondi ('i' like kite) which sounds very funny to me hahaha'.
Is This conversation is an unreal conditional sentence where If conditional clause is not said by Sam to his Australian friend and silent on this conversation?.

Kiran Pradhan

Hi Kiran,

You are right in both examples. We use 'would' when we are making a guess about something we cannot see. You can think of it as a conditional with a hidden if-clause:

That would be Sam (if I opened the door).

The second sentence also has a hidden if-clause, as you say:

An American would pronounce 'Bondi' instead of 'Bondi' (if one said it). 


Best wishes,


The LearnEnglish Team

Hi Peter and Kirk,
I just had the conversation with Panel beating guys about my car repair quote and had asked them about estimated price, and they replied me with this text message:
"Hi Kiran to repair and paint that damage would cost you $850 and we can make it look original again.
We would need the car for 3 days to complete the job. Hopefully, we can help you, Cheers! ".

Does this two sentence have silent if- clause and talking about a hypothetical situation?
It would be awesome if you guys could help me on this small confusion.


Hi kiranpn,

Yes, there is an implied or assumed condition in each sentence as they are describing hypothetical outcomes, dependent on an earlier decision.


Best wishes,


The LearnEnglish Team

Hi Peter,
Thank you for the explanation.

In my understanding, would is also used for unsure about something and just assuming. For example:

1.He would be 10 years old. (we don't know his age and just assuming)
2.David has lost his job and would be looking for a new job.(Unsure about his job search and just assuming that he is looking for a new job).
Am I right here?. Apologies for this new question again, I always get confused whether someone is talking about the hypothetical situation or unsure about something and just assuming.


Hi Kiran,

It's really a moot point. You can consider speculative sentences with 'would' of this type as having an implied if-clause, or you can simply take this as a particular use of 'would':

He would be 10 years old (if we checked).

I think it can be useful to consider the implied clause as it helps to clarify when 'would' is appropriate.

Your second sentence does not seem very likely to me. I think the past simple (completed past event) and 'will' for present speculation is much more likely:

David lost his job and will be looking for a new job.


Best wishes,


The LearnEnglish Team