We use the present perfect to show that something has continued up to the present

They’ve been married for nearly fifty years.
She has lived in Liverpool all her life.

… or is important in the present:

I’ve lost my keys. I can’t get into the house.
Teresa isn’t at home. I think she has gone shopping.

We use the present perfect continuous to show that something has been continuing up to the present:

It’s been raining for hours.
We’ve been waiting here since six o’clock this morning.

We use the past perfect to show that something continued up to a time in the past:

When George died he and Anne had been married for nearly fifty years.

... or was important at that time in the past:

I couldn’t get into the house. I had lost my keys.
Teresa wasn’t at home. She had gone shopping.

We use the past perfect continuous to show that something had been continuing up to a time in the past or was important at that time in the past:

Everything was wet. It had been raining for hours.
He was a wonderful guitarist. He had been playing ever since he was a teenager.

We use will with the perfect to show that something will be complete at some time in the future:

In a few years they will have discovered a cure for the common cold.
I can come out tonight. I'll have finished my homework by then.

We use would with the perfect to refer to something that did not happen in the past but would have happened if the conditions had been right:

If you had asked me I would have helped you.
I would have helped you, but you didn’t ask me.
You didn’t ask me or I would have helped you.

We use other modals with perfective aspect when we are looking back from a point in time when something might have happened, should have happened or would have happened.

The point of time may be in the future:

We’ll meet again next week. We might have finished the work by then.
I will phone at six o’clock. He should have got home by then.

the present:

It’s getting late. They should have arrived by now.
He’s still not here. He must have missed his train.

or the past:

I wasn’t feeling well. I must have eaten something bad.
I checked my cell phone. She could have left a message.

 


 

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Comments

Hi, could explain me correct form "She could have left a message" or it should be "She could has left a message". Thank you.

Hello Taket,

The correct form here is 'could have'. We do not use 'has' after a modal verb.

 

Best wishes,

Peter

The LearnEnglish Team

Hello,

This topic is really confusing me!

( In a few years they will have discovered a cure for the common cold.
In a few years they will discover a cure for the common cold. ) Is there a different in meaning between these sentences?

(I would have helped you, but you didn’t ask me.
I would help you, but you didn’t ask me.) Is there a different in meaning between these sentences too?

Hello Ola Jamal,

In the first pair of sentences (about the cure), there is just a slight difference of emphasis, but other than that they mean the same thing. The one with the future perfect looks back on the discovery from a point futher in the future, but for all intents and purposes otherwise they mean exactly the same thing.

In the second pair of sentences there is a difference in meaning. The sentence with 'would' speaks about a hypothetical or unreal action either now or in the future, whereas the sentence with 'would have' speaks about an unreal action in the past, i.e. an action that didn't take place. In the sentence with 'would', I could still help you, but in the one with 'would have', it is no longer possible.

Does that make sense?

All the best,
Kirk
The LearnEnglish Team

Yes, it does. Thank you Mr Kirk.

Hi, All.
I have a doubt.
How should I say: "I will phone at six o’clock. I should have got home by then" or "I will phone at six o’clock. I should get home by then"

Hello Xalmolxis,

Both forms are grammatically correct. The second one (with a simpler verb form) is probably more common in informal speaking. We also often use 'be' for the second verb ('I should be home by then').

All the best,
Kirk
The LearnEnglish Team

Hello sir , in the following sentence -
You must compare prices before you buy anything.
Both 'must compare' and 'buy' seem to be FINITE VERBS?
Though they don't change with the change of the subject to first or third person , they change with the change of the tense order. Ex. We should have 'compared' prices before we 'bought' anything.( Past )
Can a sentence be formed without a non finite verb?

Hello amrita,

I'd say 'compare' is a nonfinite verb, as it is the bare infinitive form (due to it following the modal verb 'must'), and 'buy' is clearly finite -- it has a subject ('you'). 'have compared' (in 'should have compared') is a perfective infinitive, which is also a nonfinite form.

A 'complete' sentence in English requires a subject and a verb, which means it must have a finite form.

These kinds of questions are a bit beyond the scope of what we do here at LearnEnglish, so if you have any other questions on this, I'd recommend the Wikipedia.

All the best,
Kirk
The LearnEnglish Team

Thank you sir for explaining so clearly. I shall remain ever grateful to Kirk sir and The LearnEnglish Team for helping me to understand the tricky parts of the language I love the most.

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