could know
Irregular verb: know - knew- known

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could know
you could know
he could know
we could know
you could know
they could know 	I could be knowing
you could be knowing
he could be knowing
we could be knowing
you could be knowing
they could be knowing	I could have known
you could have known
he could have known
we could have known
you could have known
they could have known	I could have been knowing
you could have been knowing
he could have been knowing
we could have been knowing
you could have been knowing
they could have been knowing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not know
you could not know
he could not know
we could not know
you could not know
they could not know 	I could not be knowing
you could not be knowing
he could not be knowing
we could not be knowing
you could not be knowing
they could not be knowing	I could not have known
you could not have known
he could not have known
we could not have known
you could not have known
they could not have known	I could not have been knowing
you could not have been knowing
he could not have been knowing
we could not have been knowing
you could not have been knowing
they could not have been knowing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I know?
could you know?
could he know?
could we know?
could you know?
could they know? 	could I be knowing?
could you be knowing?
could he be knowing?
could we be knowing?
could you be knowing?
could they be knowing? 	could I have known?
could you have known?
could he have known?
could we have known?
could you have known?
could they have known? 	could I have been knowing?
could you have been knowing?
could he have been knowing?
could we have been knowing?
could you have been knowing?
could they have been knowing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not know?
could you not know?
could he not know?
could we not know?
could you not know?
could they not know? 	could I not be knowing?
could you not be knowing?
could he not be knowing?
could we not be knowing?
could you not be knowing?
could they not be knowing? 	could I not have known?
could you not have known?
could he not have known?
could we not have known?
could you not have known?
could they not have known? 	could I not have been knowing?
could you not have been knowing?
could he not have been knowing?
could we not have been knowing?
could you not have been knowing?
could they not have been knowing?