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