could tighten
Verbo regular: tighten - tightened- tightened

Afirmação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I could tighten
you could tighten
she could tighten
we could tighten
you could tighten
they could tighten 	I could be tightening
you could be tightening
she could be tightening
we could be tightening
you could be tightening
they could be tightening	I could have tightened
you could have tightened
she could have tightened
we could have tightened
you could have tightened
they could have tightened	I could have been tightening
you could have been tightening
she could have been tightening
we could have been tightening
you could have been tightening
they could have been tightening	

Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I could not tighten
you could not tighten
she could not tighten
we could not tighten
you could not tighten
they could not tighten 	I could not be tightening
you could not be tightening
she could not be tightening
we could not be tightening
you could not be tightening
they could not be tightening	I could not have tightened
you could not have tightened
she could not have tightened
we could not have tightened
you could not have tightened
they could not have tightened	I could not have been tightening
you could not have been tightening
she could not have been tightening
we could not have been tightening
you could not have been tightening
they could not have been tightening	

Forma interrogativa 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
could I tighten?
could you tighten?
could she tighten?
could we tighten?
could you tighten?
could they tighten? 	could I be tightening?
could you be tightening?
could she be tightening?
could we be tightening?
could you be tightening?
could they be tightening? 	could I have tightened?
could you have tightened?
could she have tightened?
could we have tightened?
could you have tightened?
could they have tightened? 	could I have been tightening?
could you have been tightening?
could she have been tightening?
could we have been tightening?
could you have been tightening?
could they have been tightening? 	

Forma interro-Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
could I not tighten?
could you not tighten?
could she not tighten?
could we not tighten?
could you not tighten?
could they not tighten? 	could I not be tightening?
could you not be tightening?
could she not be tightening?
could we not be tightening?
could you not be tightening?
could they not be tightening? 	could I not have tightened?
could you not have tightened?
could she not have tightened?
could we not have tightened?
could you not have tightened?
could they not have tightened? 	could I not have been tightening?
could you not have been tightening?
could she not have been tightening?
could we not have been tightening?
could you not have been tightening?
could they not have been tightening?