could tighten
Verbo regular: tighten - tightened- tightened

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I could tighten
you could tighten
he could tighten
we could tighten
you could tighten
they could tighten 	I could be tightening
you could be tightening
he could be tightening
we could be tightening
you could be tightening
they could be tightening	I could have tightened
you could have tightened
he 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
he could have been tightening
we could have been tightening
you could have been tightening
they could have been tightening	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I couldn't tighten
you couldn't tighten
he couldn't tighten
we couldn't tighten
you couldn't tighten
they couldn't tighten 	I couldn't be tightening
you couldn't be tightening
he couldn't be tightening
we couldn't be tightening
you couldn't be tightening
they couldn't be tightening	I couldn't have tightened
you couldn't have tightened
he couldn't have tightened
we couldn't have tightened
you couldn't have tightened
they couldn't have tightened	I couldn't have been tightening
you couldn't have been tightening
he couldn't have been tightening
we couldn't have been tightening
you couldn't have been tightening
they couldn't have been tightening	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
could I tighten?
could you tighten?
could he tighten?
could we tighten?
could you tighten?
could they tighten? 	could I be tightening?
could you be tightening?
could he be tightening?
could we be tightening?
could you be tightening?
could they be tightening? 	could I have tightened?
could you have tightened?
could he 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 he have been tightening?
could we have been tightening?
could you have been tightening?
could they have been tightening? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
couldn't I tighten?
couldn't you tighten?
couldn't he tighten?
couldn't we tighten?
couldn't you tighten?
couldn't they tighten? 	couldn't I be tightening?
couldn't you be tightening?
couldn't he be tightening?
couldn't we be tightening?
couldn't you be tightening?
couldn't they be tightening? 	couldn't I have tightened?
couldn't you have tightened?
couldn't he have tightened?
couldn't we have tightened?
couldn't you have tightened?
couldn't they have tightened? 	couldn't I have been tightening?
couldn't you have been tightening?
couldn't he have been tightening?
couldn't we have been tightening?
couldn't you have been tightening?
couldn't they have been tightening?