Warning, this verb may not exist. Conjugation is given as example.
Affirmation
Simple form
I could whiter you could whiter she could whiter we could whiter you could whiter they could whiter
V-ing form
I could be whitering you could be whitering she could be whitering we could be whitering you could be whitering they could be whitering
Perfect
I could have whitered you could have whitered she could have whitered we could have whitered you could have whitered they could have whitered
V-ing perfect
I could have been whitering you could have been whitering she could have been whitering we could have been whitering you could have been whitering they could have been whitering
Negation
Simple form
I couldn't whiter you couldn't whiter she couldn't whiter we couldn't whiter you couldn't whiter they couldn't whiter
V-ing form
I couldn't be whitering you couldn't be whitering she couldn't be whitering we couldn't be whitering you couldn't be whitering they couldn't be whitering
Perfect
I couldn't have whitered you couldn't have whitered she couldn't have whitered we couldn't have whitered you couldn't have whitered they couldn't have whitered
V-ing perfect
I couldn't have been whitering you couldn't have been whitering she couldn't have been whitering we couldn't have been whitering you couldn't have been whitering they couldn't have been whitering
Interrogative form
Simple form
could I whiter? could you whiter? could she whiter? could we whiter? could you whiter? could they whiter?
V-ing form
could I be whitering? could you be whitering? could she be whitering? could we be whitering? could you be whitering? could they be whitering?
Perfect
could I have whitered? could you have whitered? could she have whitered? could we have whitered? could you have whitered? could they have whitered?
V-ing perfect
could I have been whitering? could you have been whitering? could she have been whitering? could we have been whitering? could you have been whitering? could they have been whitering?
Interro-negative form
Simple form
couldn't I whiter? couldn't you whiter? couldn't she whiter? couldn't we whiter? couldn't you whiter? couldn't they whiter?
V-ing form
couldn't I be whitering? couldn't you be whitering? couldn't she be whitering? couldn't we be whitering? couldn't you be whitering? couldn't they be whitering?
Perfect
couldn't I have whitered? couldn't you have whitered? couldn't she have whitered? couldn't we have whitered? couldn't you have whitered? couldn't they have whitered?
V-ing perfect
couldn't I have been whitering? couldn't you have been whitering? couldn't she have been whitering? couldn't we have been whitering? couldn't you have been whitering? couldn't they have been whitering?