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