I can regain you can regain he can regain we can regain you can regain they can regain
V-ing form
I can be regaining you can be regaining he can be regaining we can be regaining you can be regaining they can be regaining
Perfect
I can have regained you can have regained he can have regained we can have regained you can have regained they can have regained
V-ing perfect
I can have been regaining you can have been regaining he can have been regaining we can have been regaining you can have been regaining they can have been regaining
Negation
Simple form
I can't regain you can't regain he can't regain we can't regain you can't regain they can't regain
V-ing form
I can't be regaining you can't be regaining he can't be regaining we can't be regaining you can't be regaining they can't be regaining
Perfect
I can't have regained you can't have regained he can't have regained we can't have regained you can't have regained they can't have regained
V-ing perfect
I can't have been regaining you can't have been regaining he can't have been regaining we can't have been regaining you can't have been regaining they can't have been regaining
Interrogative form
Simple form
can I regain? can you regain? can he regain? can we regain? can you regain? can they regain?
V-ing form
can I be regaining? can you be regaining? can he be regaining? can we be regaining? can you be regaining? can they be regaining?
Perfect
can I have regained? can you have regained? can he have regained? can we have regained? can you have regained? can they have regained?
V-ing perfect
can I have been regaining? can you have been regaining? can he have been regaining? can we have been regaining? can you have been regaining? can they have been regaining?
Interro-negative form
Simple form
can't I regain? can't you regain? can't he regain? can't we regain? can't you regain? can't they regain?
V-ing form
can't I be regaining? can't you be regaining? can't he be regaining? can't we be regaining? can't you be regaining? can't they be regaining?
Perfect
can't I have regained? can't you have regained? can't he have regained? can't we have regained? can't you have regained? can't they have regained?
V-ing perfect
can't I have been regaining? can't you have been regaining? can't he have been regaining? can't we have been regaining? can't you have been regaining? can't they have been regaining?