English verb conjugation
CAN RIFF

Regular verb: riff - riffed - riffed

Affirmation

Simple form	V-ing form
I can riff you can riff he can riff we can riff you can riff they can riff	I can be riffing you can be riffing he can be riffing we can be riffing you can be riffing they can be riffing
Perfect	V-ing perfect
I can have riffed you can have riffed he can have riffed we can have riffed you can have riffed they can have riffed	I can have been riffing you can have been riffing he can have been riffing we can have been riffing you can have been riffing they can have been riffing

Negation

Simple form	V-ing form
I cannot riff you cannot riff he cannot riff we cannot riff you cannot riff they cannot riff	I cannot be riffing you cannot be riffing he cannot be riffing we cannot be riffing you cannot be riffing they cannot be riffing
Perfect	V-ing perfect
I cannot have riffed you cannot have riffed he cannot have riffed we cannot have riffed you cannot have riffed they cannot have riffed	I cannot have been riffing you cannot have been riffing he cannot have been riffing we cannot have been riffing you cannot have been riffing they cannot have been riffing

Interrogative form

Simple form	V-ing form
can I riff? can you riff? can he riff? can we riff? can you riff? can they riff?	can I be riffing? can you be riffing? can he be riffing? can we be riffing? can you be riffing? can they be riffing?
Perfect	V-ing perfect
can I have riffed? can you have riffed? can he have riffed? can we have riffed? can you have riffed? can they have riffed?	can I have been riffing? can you have been riffing? can he have been riffing? can we have been riffing? can you have been riffing? can they have been riffing?

Interro-negative form

Simple form	V-ing form
can I not riff? can you not riff? can he not riff? can we not riff? can you not riff? can they not riff?	can I not be riffing? can you not be riffing? can he not be riffing? can we not be riffing? can you not be riffing? can they not be riffing?
Perfect	V-ing perfect
can I not have riffed? can you not have riffed? can he not have riffed? can we not have riffed? can you not have riffed? can they not have riffed?	can I not have been riffing? can you not have been riffing? can he not have been riffing? can we not have been riffing? can you not have been riffing? can they not have been riffing?