could sue
Regular verb: sue - sued- sued

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could sue
you could sue
she could sue
we could sue
you could sue
they could sue 	I could be suing
you could be suing
she could be suing
we could be suing
you could be suing
they could be suing	I could have sued
you could have sued
she could have sued
we could have sued
you could have sued
they could have sued	I could have been suing
you could have been suing
she could have been suing
we could have been suing
you could have been suing
they could have been suing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not sue
you could not sue
she could not sue
we could not sue
you could not sue
they could not sue 	I could not be suing
you could not be suing
she could not be suing
we could not be suing
you could not be suing
they could not be suing	I could not have sued
you could not have sued
she could not have sued
we could not have sued
you could not have sued
they could not have sued	I could not have been suing
you could not have been suing
she could not have been suing
we could not have been suing
you could not have been suing
they could not have been suing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I sue?
could you sue?
could she sue?
could we sue?
could you sue?
could they sue? 	could I be suing?
could you be suing?
could she be suing?
could we be suing?
could you be suing?
could they be suing? 	could I have sued?
could you have sued?
could she have sued?
could we have sued?
could you have sued?
could they have sued? 	could I have been suing?
could you have been suing?
could she have been suing?
could we have been suing?
could you have been suing?
could they have been suing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not sue?
could you not sue?
could she not sue?
could we not sue?
could you not sue?
could they not sue? 	could I not be suing?
could you not be suing?
could she not be suing?
could we not be suing?
could you not be suing?
could they not be suing? 	could I not have sued?
could you not have sued?
could she not have sued?
could we not have sued?
could you not have sued?
could they not have sued? 	could I not have been suing?
could you not have been suing?
could she not have been suing?
could we not have been suing?
could you not have been suing?
could they not have been suing?