could understand
Irregular verb: understand - understood- understood

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could understand
you could understand
he could understand
we could understand
you could understand
they could understand 	I could be understanding
you could be understanding
he could be understanding
we could be understanding
you could be understanding
they could be understanding	I could have understood
you could have understood
he could have understood
we could have understood
you could have understood
they could have understood	I could have been understanding
you could have been understanding
he could have been understanding
we could have been understanding
you could have been understanding
they could have been understanding	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not understand
you could not understand
he could not understand
we could not understand
you could not understand
they could not understand 	I could not be understanding
you could not be understanding
he could not be understanding
we could not be understanding
you could not be understanding
they could not be understanding	I could not have understood
you could not have understood
he could not have understood
we could not have understood
you could not have understood
they could not have understood	I could not have been understanding
you could not have been understanding
he could not have been understanding
we could not have been understanding
you could not have been understanding
they could not have been understanding	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I understand?
could you understand?
could he understand?
could we understand?
could you understand?
could they understand? 	could I be understanding?
could you be understanding?
could he be understanding?
could we be understanding?
could you be understanding?
could they be understanding? 	could I have understood?
could you have understood?
could he have understood?
could we have understood?
could you have understood?
could they have understood? 	could I have been understanding?
could you have been understanding?
could he have been understanding?
could we have been understanding?
could you have been understanding?
could they have been understanding? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not understand?
could you not understand?
could he not understand?
could we not understand?
could you not understand?
could they not understand? 	could I not be understanding?
could you not be understanding?
could he not be understanding?
could we not be understanding?
could you not be understanding?
could they not be understanding? 	could I not have understood?
could you not have understood?
could he not have understood?
could we not have understood?
could you not have understood?
could they not have understood? 	could I not have been understanding?
could you not have been understanding?
could he not have been understanding?
could we not have been understanding?
could you not have been understanding?
could they not have been understanding?