can tighten
Regular verb: tighten - tightened- tightened

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I can tighten
you can tighten
she can tighten
we can tighten
you can tighten
they can tighten 	I can be tightening
you can be tightening
she can be tightening
we can be tightening
you can be tightening
they can be tightening	I can have tightened
you can have tightened
she can have tightened
we can have tightened
you can have tightened
they can have tightened	I can have been tightening
you can have been tightening
she can have been tightening
we can have been tightening
you can have been tightening
they can have been tightening	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I cannot tighten
you cannot tighten
she cannot tighten
we cannot tighten
you cannot tighten
they cannot tighten 	I cannot be tightening
you cannot be tightening
she cannot be tightening
we cannot be tightening
you cannot be tightening
they cannot be tightening	I cannot have tightened
you cannot have tightened
she cannot have tightened
we cannot have tightened
you cannot have tightened
they cannot have tightened	I cannot have been tightening
you cannot have been tightening
she cannot have been tightening
we cannot have been tightening
you cannot have been tightening
they cannot have been tightening	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can I tighten?
can you tighten?
can she tighten?
can we tighten?
can you tighten?
can they tighten? 	can I be tightening?
can you be tightening?
can she be tightening?
can we be tightening?
can you be tightening?
can they be tightening? 	can I have tightened?
can you have tightened?
can she have tightened?
can we have tightened?
can you have tightened?
can they have tightened? 	can I have been tightening?
can you have been tightening?
can she have been tightening?
can we have been tightening?
can you have been tightening?
can they have been tightening? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can I not tighten?
can you not tighten?
can she not tighten?
can we not tighten?
can you not tighten?
can they not tighten? 	can I not be tightening?
can you not be tightening?
can she not be tightening?
can we not be tightening?
can you not be tightening?
can they not be tightening? 	can I not have tightened?
can you not have tightened?
can she not have tightened?
can we not have tightened?
can you not have tightened?
can they not have tightened? 	can I not have been tightening?
can you not have been tightening?
can she not have been tightening?
can we not have been tightening?
can you not have been tightening?
can they not have been tightening?