Warning, this verb may not exist. Conjugation is given as example.
Affirmation
Simple form
I could warn warn you could warn warn he could warn warn we could warn warn you could warn warn they could warn warn
V-ing form
I could be warn warning you could be warn warning he could be warn warning we could be warn warning you could be warn warning they could be warn warning
Perfect
I could have warn warned you could have warn warned he could have warn warned we could have warn warned you could have warn warned they could have warn warned
V-ing perfect
I could have been warn warning you could have been warn warning he could have been warn warning we could have been warn warning you could have been warn warning they could have been warn warning
Negation
Simple form
I could not warn warn you could not warn warn he could not warn warn we could not warn warn you could not warn warn they could not warn warn
V-ing form
I could not be warn warning you could not be warn warning he could not be warn warning we could not be warn warning you could not be warn warning they could not be warn warning
Perfect
I could not have warn warned you could not have warn warned he could not have warn warned we could not have warn warned you could not have warn warned they could not have warn warned
V-ing perfect
I could not have been warn warning you could not have been warn warning he could not have been warn warning we could not have been warn warning you could not have been warn warning they could not have been warn warning
Interrogative form
Simple form
could I warn warn? could you warn warn? could he warn warn? could we warn warn? could you warn warn? could they warn warn?
V-ing form
could I be warn warning? could you be warn warning? could he be warn warning? could we be warn warning? could you be warn warning? could they be warn warning?
Perfect
could I have warn warned? could you have warn warned? could he have warn warned? could we have warn warned? could you have warn warned? could they have warn warned?
V-ing perfect
could I have been warn warning? could you have been warn warning? could he have been warn warning? could we have been warn warning? could you have been warn warning? could they have been warn warning?
Interro-negative form
Simple form
could I not warn warn? could you not warn warn? could he not warn warn? could we not warn warn? could you not warn warn? could they not warn warn?
V-ing form
could I not be warn warning? could you not be warn warning? could he not be warn warning? could we not be warn warning? could you not be warn warning? could they not be warn warning?
Perfect
could I not have warn warned? could you not have warn warned? could he not have warn warned? could we not have warn warned? could you not have warn warned? could they not have warn warned?
V-ing perfect
could I not have been warn warning? could you not have been warn warning? could he not have been warn warning? could we not have been warn warning? could you not have been warn warning? could they not have been warn warning?