Does anyone tell me how and when we will use these sentences?

[shahjahan]

There is a word should.When we will use it and in which place we

will use should.on which place and which type of sentence we will us should

+first form.When we will use should+have+3rd form of verb.I want to when

we will use could+have/has+3rd and in which sentence.I want knot when we

will use would+1st form and when we will use would+has/have+3rd form and

in which type of sentences.in which sentence we will use have been/has

been+3rd or 4th form i mean in present or future.I want to know and learn all

these sentences please tell me how we will use it and apply it?

THANKS

 

[Horsa]

"Should" is a modal verb. It is used for giving advice or criticism. Because "should" is a modal verb the verb that follows it in a sentence is always first form but never third person (e.g. goes):

a) I think she should go.
b) I think she should have gone. (never has)

Should + infinitive without to as in sentence (a) above means now or in the future:

c) I think she should go now.
d) I think she should go tomorrow.

Should + present perfect as in sentence (b) is a criticism of something someone did or didn't do in the past:

e) I think she should have gone to the hospital to visit her grandmother yesterday. (but she didn't)


"Could" follows the same rules as "should" and is used to talk about possibility/opportunity:

f) You could go now (if you want to).
g) You could have gone last week. (You had the opportunity to do so, but didn't use it).


"Would" follows the same rules as "should" and "could" and is used to talk about a person's willingness to do something:

h) I would go with him tomorrow but I can't because I have an exam.
i) I would have gone with him yesterday, but he said he wanted to go alone.