I can function you can function he can function we can function you can function they can function
V-ing form
I can be functioning you can be functioning he can be functioning we can be functioning you can be functioning they can be functioning
Perfect
I can have functioned you can have functioned he can have functioned we can have functioned you can have functioned they can have functioned
V-ing perfect
I can have been functioning you can have been functioning he can have been functioning we can have been functioning you can have been functioning they can have been functioning
Negation
Simple form
I cannot function you cannot function he cannot function we cannot function you cannot function they cannot function
V-ing form
I cannot be functioning you cannot be functioning he cannot be functioning we cannot be functioning you cannot be functioning they cannot be functioning
Perfect
I cannot have functioned you cannot have functioned he cannot have functioned we cannot have functioned you cannot have functioned they cannot have functioned
V-ing perfect
I cannot have been functioning you cannot have been functioning he cannot have been functioning we cannot have been functioning you cannot have been functioning they cannot have been functioning
Interrogative form
Simple form
can I function? can you function? can he function? can we function? can you function? can they function?
V-ing form
can I be functioning? can you be functioning? can he be functioning? can we be functioning? can you be functioning? can they be functioning?
Perfect
can I have functioned? can you have functioned? can he have functioned? can we have functioned? can you have functioned? can they have functioned?
V-ing perfect
can I have been functioning? can you have been functioning? can he have been functioning? can we have been functioning? can you have been functioning? can they have been functioning?
Interro-negative form
Simple form
can I not function? can you not function? can he not function? can we not function? can you not function? can they not function?
V-ing form
can I not be functioning? can you not be functioning? can he not be functioning? can we not be functioning? can you not be functioning? can they not be functioning?
Perfect
can I not have functioned? can you not have functioned? can he not have functioned? can we not have functioned? can you not have functioned? can they not have functioned?
V-ing perfect
can I not have been functioning? can you not have been functioning? can he not have been functioning? can we not have been functioning? can you not have been functioning? can they not have been functioning?