Modal Verbs
Modals Characteristics
Don't use "S" third person sinular
Make questions by inversion (she can go -> can she go?)
Followed directly by infinitive of another verb
Always combined with another verb in the base form
Can (Present)
To express an ability to do something
To make general statements about what is possible
To express a permission or offer, to say that something is allowed
To express something that is forbidden or an inability to do something
To say that something is impossible
Could (can past)
Used with see, hear,smell, taste, feel, remember, understand
To say that somebody had the general ability or permission to do something
Use was/were able to to say tha somebody did something in a specific situation
Negative = Can not/Can't
Negative = Couldn't/ Could not
Be used for polite request, an ability, a possibility and a polite suggestion
Must
To say that you believe something is certain
For the past we use must have (done)
To express obligation ( personal opinion - the obligation comes from the speaker)
Use Have to do to say what someone is obliged to do (speaker not giving his/her own opinion)
Can not use must to talk about the past or the futur
Mustn't do something = you do not do it (so don't do it) - interdiction >< Don't have to do something you don't need to do it (but you can if you want)
May/Might
Should
The negative form is may not
The negative form of might is might not/mightn't
To say that something is possible
For the past we use may have (done) or might have (done)
Could = may and might
Couldn't different from may not and might not
To talk about possible actions or happenings in the future
May to ask for, to give or to refuse permission
For the past/future we use to be allowed to
The negative form is shouldn't or should not
You should do something = it is a good thing to do or the right thing to do. To give advice or to give an opinion
To express that a situation is likely in the present/future
You shouldn't do something = it isn't a good thing to do
Should is not as strong as must or have to
You should have done something = you didn't do it, but it would have been the right thing to do
You shouldn't have done something = you did it, but it was the wrong thing to do