English Grammar | Modals / Can

Modals of Can

1) Can:

Spelling:

 

can, can't, cannot.

Uses: 

can has five possible uses: Ability, Permission, Negative deduction ; GENERAL Possibility; particular possibility.

A/ Ability : 

Can in the sense of ability has three possible forms:

a/ Present : 

He can go ( he is able to go ).

b/ Past/Condition : type 2 : 

He could go ( he was able to go / he would be able to go ).

c/ Condition  : type 3 : 

He could have gone ( he would have been able to go ).

All other tenses are formed with Be Able to, future : He will be able to....
Present : He has been able to...

B/ Difference between Was and Could : were able to : 

Sometimes there is no difference between Could and Was : were able to and both can be used without any difference in meaning. The only difference is that Could expresses general post ability ( used past ability ) whereas Was able the expresses Particular past ability and past achievement. It refers to ability in precise situation, in other words I was able to do it = I could do it and I did it. It can be replaced by I managed to do it or I succeed in doing it.

Example:

a) He could

drive very well when he was young. ( General last ability ).
b) Though he was tired, he was able to swim to the shore. ( Particular past ability ).

Remark:

In the negative form this distinction doesn't apply and couldn't can be used for particular past ability.

Example in contrast :

- The box was locked, and I couldn't open it. ( Particular past ability )

- Although the door was locked, I was able to open it. ( Particular past ability ).

B/ Permission : 

Can in the sense of permission has to forms :

1) Present/ Future : He can go ( he may go, He is allowed to go or he will be allowed to go...).

2) Past/ Condition. Type 2 : He could go ( He was allowed to go/ He would be All to go....).

All the other tenses are formed with BE ALLOWED To.

- Present perfect : She has been allowed to.....

- Past perfect : She She had been allowed to.....

- Condition. Type 3 : She would have been allowed to.....

Examples:

Present: 

Affirmative : You can borrow my car if you want to (you may borrow it / I allow you t....).

Informative : ( can = could = may ).

a) can / could / may I borrow you dictionary? ( Could is past form but the meaning is present).
b) yes, you can. ( Don't say: yes, you could. Could is more hesitant that can, with could you are not sure you will get the permission.

Negative ( can't = mustn't )
c) you can't get into a mosque with your shoes on. ( It's forbidden, you mustn't, you're not allowed....).