I could come you could come he could come we could come you could come they could come
V-ing form
I could be coming you could be coming he could be coming we could be coming you could be coming they could be coming
Perfect
I could have come you could have come he could have come we could have come you could have come they could have come
V-ing perfect
I could have been coming you could have been coming he could have been coming we could have been coming you could have been coming they could have been coming
Negation
Simple form
I could not come you could not come he could not come we could not come you could not come they could not come
V-ing form
I could not be coming you could not be coming he could not be coming we could not be coming you could not be coming they could not be coming
Perfect
I could not have come you could not have come he could not have come we could not have come you could not have come they could not have come
V-ing perfect
I could not have been coming you could not have been coming he could not have been coming we could not have been coming you could not have been coming they could not have been coming
Interrogative form
Simple form
could I come? could you come? could he come? could we come? could you come? could they come?
V-ing form
could I be coming? could you be coming? could he be coming? could we be coming? could you be coming? could they be coming?
Perfect
could I have come? could you have come? could he have come? could we have come? could you have come? could they have come?
V-ing perfect
could I have been coming? could you have been coming? could he have been coming? could we have been coming? could you have been coming? could they have been coming?
Interro-negative form
Simple form
could I not come? could you not come? could he not come? could we not come? could you not come? could they not come?
V-ing form
could I not be coming? could you not be coming? could he not be coming? could we not be coming? could you not be coming? could they not be coming?
Perfect
could I not have come? could you not have come? could he not have come? could we not have come? could you not have come? could they not have come?
V-ing perfect
could I not have been coming? could you not have been coming? could he not have been coming? could we not have been coming? could you not have been coming? could they not have been coming?