can riff
Regular verb: riff - riffed- riffed

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