Past+Modals

e.g. I can't have lost my keys! (I'm sure I didn't) ||
 * ** can't have ** ||  certainty

|| ** could **
 * permission e.g. When I was a teenager, I could go out as late as I wanted. ||
 * || general ability  e.g. Tom could walk by the age of 8 months. ||

|| ** could have ** || ** couldn't **
 * possibility, but did not happen e.g. I could have passed my driving test if I'd really tried. ||
 * || uncertainty  e.g. I guess it could have been Sandra on the phone. ||
 * permission e.g. When I was a teenager, I couldn't stay out as late as I wanted. ||
 * || general ability  e.g. I couldn't walk until I was 2. ||
 * || ability in a particular situation  e.g. I tried hard but I couldn't persuade him to go to the party with us. ||

|| ** couldn't have ** || possibility/ability  e.g. I couldn't possibly have passed my driving test, even if I'd tried harder. e.g. I couldn't have left the dog in the car for long (so I didn't). || || ** didn’t need to ** e.g. As I was alone this weekend, I didn't need to do any cooking (so I didn't). ||
 * || uncertainty  e.g. It couldn't have been Sandra on the phone, could it? ||
 * || with comparative adjectives  e.g. I couldn't have asked for better weather on my wedding day. ||
 * ||  unwillingness
 * ||  unwillingness
 * unnecessary action not done

|| ** had to ** e.g. I couldn't go out last night because I had to do my homework. ||
 * obligation (past form of //must//)

|| ** may have ** e.g. I guess I may have been a bit hard on her when she came home an hour late. ||
 * uncertainty

|| ** may not have ** e.g. He may not have found out yet that he has passed the test. ||
 * uncertainty

|| ** might have **
 * possibility (didn't happen) e.g. You might have been killed! ||
 * || uncertainty  e.g. I guess I might have been a bit hard on her when she came home an hour late. ||
 * || annoyance at someone's failure to do something  e.g. You __might__ have __told__ me that you had invited all your colleagues round for dinner! ||
 * || might have known + would (idiom to ironically express that somebody's action was typical)  e.g. I might have known that he would finish with me as soon as he found out I wasn't wealthy! ||

|| ** might not have ** e.g. He may not have found out yet that he has passed the test. ||
 * uncertainty

|| ** must have **
 * certainty e.g. He must have known how much it was going to cost. (I'm sure he knew.) ||
 * || with //surely// in exclamations  e.g. Surely he must have known how much it was going to cost! ||

|| ** needn't have **
 * unnecessary action that was actually done e.g. Oh, you needn't have done the washing up! ||

|| ** ought not to have ** e.g. You ought not to have been so frank with him. ||
 * criticism (more common is //shouldn't have//)

|| ** ought to have ** Why is she late? She ought to have arrived by now! ||
 * expectation (//should have// is more common)

|| ** should have ** Why is she late? She should have arrived by now! ||
 * expectation
 * || should have + verbs of thinking  e.g. I should have thought you knew. ||
 * || with //be// and adjectives, describing chance  e.g. It was weird that you should have been staying in the same hostel last month. ||
 * || criticism (you didn't do something, but it would have been the right thing to do)  e.g. The party was such fun last night! You should have come! ||

|| ** shouldn't have ** e.g. You shouldn ' t have been so frank with him. || "Here's a bottle of wine for you" "Oh, you really shouldn't have!" ||
 * criticism
 * ||  polite expression of thanks on receiving a gift or favour

|| ** would have **
 * events in the past that did not happen e.g. I wouldn't have gone out with him, but he didn't ask me. ||
 * || assumptions  e.g. Oh, that would have been Sarah on the phone just now. ||

|| ** would not ** || unwillingness  e.g. I asked Tom to close the window, but he wouldn't do it.

Reference []


 * **should and should have, would and would have, could and could have** ||
 * [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="56" height="1"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="333" height="1"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="106" height="1"]] ||

Could you please explain the difference between the modal auxiliary verbs **should, could** and **would** and how they are used? Thanks for your help. **Asim** from **Pakistan** writes: I still feel some complication in understanding these modals: **would have, should have** and **could have**. Please give me some examples to help me understand. ||
 * [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="1" height="10"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="5" height="1"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="1" height="1"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="10" height="1"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="333" height="1"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/learnit195_100x120.jpg width="100" height="120" caption="Athlete"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="6" height="1"]] ||
 * [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="1" height="125"]] ||^  || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/question_4040.gif width="40"]] ||^   ||^   ||^   || **Danilo Gomez Barbosa** from **Columbia** writes:


 * [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="55" height="1"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="333" height="1"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="106" height="1"]] ||
 * [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="56" height="1"]] || **Roger Woodham** replies:  ||   ||
 * [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="1" height="2"]] ||

> >
 * [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="6" height="1"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="40" height="10"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="10" height="1"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="433" height="1"]] ||
 * ^  || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/answer_4040.gif width="40" height="40"]] ||^   || **should**
 * Should** is used to give advice and make recommendations and to talk about obligation, duty and what is expected to happen. Reference is to the present and the future. **Should** is similar to **must** but is not as strong as **must**:
 * **//You should//** //always wear a **helmet** when you go out cycling on busy roads.//
 * //Once the pack is opened, the cooked meat inside **should** **be** **consumed** within three days.//
 * //**Should I tell her** that her son is playing truant and skipping school? ~ I think **you should**. **She should know** about it.// ||

Should combines with the perfect infinitive to form **should have** + past participle when we want to talk about **past events that did not happen**, but **should have happened**. We are talking about an expectation and referring back to past time. Compare the following: Before Tom leaves for work, his wife advises him: > > But it did rain. When he arrives back home, his wife says: > > > Reference to the present and future: > > > Reference to the past: >
 * [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="6" height="1"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="40" height="10"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="10" height="8"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="433" height="1"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="6" height="1"]] ||
 * ^  || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="1" height="40"]] ||   |||| **should and should have**
 * //**You should take** your umbrella. It might rain. ~ No, I'll be all right. I shan't need it.//
 * //What did I tell you? **You should have taken** your umbrella. Then you wouldn't have got wet.//
 * **//You should try//** //and smoke less, Henry. Your health isn't very good and it's getting worse.//
 * //**I should have** given up smoking years ago, Mary. If I had, I wouldn't be in such bad shape now.// ||

If we want to talk about an unreal or unlikely situation that might arise now or in the future, we use a **past tense** in the **if-clause** and **would + infinitive** in the **main clause**. Compare the following and note that **would** is often abbreviated to **'d**: If we want to refer to the past and make a statement about things that did not happen, we need to use **had + past participle** in the **if clause** and **would have** constructions in the **main clause.** Note in these sentences that we can use **'d** as the abbreviation for both **had** in the if-clause and **would** in the main clause: >
 * [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="6" height="1"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="40" height="10"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="10" height="8"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="433" height="1"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="6" height="1"]] ||
 * ^  || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="1" height="40"]] ||   |||| **would**
 * //How **would you manage**, if I wasn't here to help you? ~ **I'd manage** somehow. **I wouldn't bother** to cook. **I'd go out** to eat or bring home a take-away. **I'd ask** your mother to help me with the washing and the ironing. I know **she'd help** me.//
 * would have**
 * //If he'd taken an umbrella, **he wouldn't have got** wet on the way home.//
 * //If he'd taken his umbrella, **he'd have stayed** dry.// ||

> > As with **would have**, and **should have, could have** is used to talk about the past and refers to things that people could have done in the past, but didn't attempt to do or succeed in doing: > Note the difference between **would have** and **could have** in the following two examples. **Would have** indicates certainty that he would have won if he had tried harder, **could have** indicates that it is a possibility. **Might have** is similar in meaning to could have, although the possibility is perhaps not quite as great: * //If he'd tried a bit harder, **he would have won** the race. > // > Note the way in which all three of these modals are combined in these exchanges which refer to a meeting that has just taken place:
 * [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="6" height="1"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="40" height="10"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="10" height="8"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="433" height="1"]] || [[image:http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/images/furniture/clear.gif width="6" height="1"]] ||
 * ^  ||   ||   |||| **could**
 * Could** can be used to ask for permission, to make a request and express ability in the past. Compare the following:
 * //**Could I** borrow your black dress for the formal dinner tomorrow? ~ Of course you can!//
 * //**Could you** do me a favour and pick Pete up from the station? ~ Of course I will!//
 * //**I could** already **swim** by the time I was three. ~ Could you really? I couldn't swim until I was eight.//
 * could have**
 * **//I could have gone//** //to university, if I'd passed my exams.//
 * //If he'd trained harder, I'm sure **he could have** **completed** the swim.//|| 
 * //If he'd tried a bit harder, **he could have won** the race.//
 * //If he'd tried a bit harder, **he might have won** the// <span style="font-family: Verdana,Arial,Helvetica,sans-serif;">//race.// || ||
 * ^  ||   ||   |||| **should have / could have / wouldn't have**
 * //Why did you come to the meeting? It didn't need both of us. **You should have known** that I would be there. ~ **How could I have known** you'd be there? I haven't spoken to you for a fortnight! ~ If I'd known you were intending to go, **I certainly wouldn't have gone**!// ||

Reference []

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