could weaken
Verbo regular: weaken - weakened- weakened

Afirmação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I could weaken
you could weaken
she could weaken
we could weaken
you could weaken
they could weaken 	I could be weakening
you could be weakening
she could be weakening
we could be weakening
you could be weakening
they could be weakening	I could have weakened
you could have weakened
she could have weakened
we could have weakened
you could have weakened
they could have weakened	I could have been weakening
you could have been weakening
she could have been weakening
we could have been weakening
you could have been weakening
they could have been weakening	

Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I could not weaken
you could not weaken
she could not weaken
we could not weaken
you could not weaken
they could not weaken 	I could not be weakening
you could not be weakening
she could not be weakening
we could not be weakening
you could not be weakening
they could not be weakening	I could not have weakened
you could not have weakened
she could not have weakened
we could not have weakened
you could not have weakened
they could not have weakened	I could not have been weakening
you could not have been weakening
she could not have been weakening
we could not have been weakening
you could not have been weakening
they could not have been weakening	

Forma interrogativa 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
could I weaken?
could you weaken?
could she weaken?
could we weaken?
could you weaken?
could they weaken? 	could I be weakening?
could you be weakening?
could she be weakening?
could we be weakening?
could you be weakening?
could they be weakening? 	could I have weakened?
could you have weakened?
could she have weakened?
could we have weakened?
could you have weakened?
could they have weakened? 	could I have been weakening?
could you have been weakening?
could she have been weakening?
could we have been weakening?
could you have been weakening?
could they have been weakening? 	

Forma interro-Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
could I not weaken?
could you not weaken?
could she not weaken?
could we not weaken?
could you not weaken?
could they not weaken? 	could I not be weakening?
could you not be weakening?
could she not be weakening?
could we not be weakening?
could you not be weakening?
could they not be weakening? 	could I not have weakened?
could you not have weakened?
could she not have weakened?
could we not have weakened?
could you not have weakened?
could they not have weakened? 	could I not have been weakening?
could you not have been weakening?
could she not have been weakening?
could we not have been weakening?
could you not have been weakening?
could they not have been weakening?