could yada-yada
Regular verb: yada-yada - yada-yadaed- yada-yadaed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could yada-yada
you could yada-yada
he could yada-yada
we could yada-yada
you could yada-yada
they could yada-yada 	I could be yada-yadaing
you could be yada-yadaing
he could be yada-yadaing
we could be yada-yadaing
you could be yada-yadaing
they could be yada-yadaing	I could have yada-yadaed
you could have yada-yadaed
he could have yada-yadaed
we could have yada-yadaed
you could have yada-yadaed
they could have yada-yadaed	I could have been yada-yadaing
you could have been yada-yadaing
he could have been yada-yadaing
we could have been yada-yadaing
you could have been yada-yadaing
they could have been yada-yadaing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not yada-yada
you could not yada-yada
he could not yada-yada
we could not yada-yada
you could not yada-yada
they could not yada-yada 	I could not be yada-yadaing
you could not be yada-yadaing
he could not be yada-yadaing
we could not be yada-yadaing
you could not be yada-yadaing
they could not be yada-yadaing	I could not have yada-yadaed
you could not have yada-yadaed
he could not have yada-yadaed
we could not have yada-yadaed
you could not have yada-yadaed
they could not have yada-yadaed	I could not have been yada-yadaing
you could not have been yada-yadaing
he could not have been yada-yadaing
we could not have been yada-yadaing
you could not have been yada-yadaing
they could not have been yada-yadaing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I yada-yada?
could you yada-yada?
could he yada-yada?
could we yada-yada?
could you yada-yada?
could they yada-yada? 	could I be yada-yadaing?
could you be yada-yadaing?
could he be yada-yadaing?
could we be yada-yadaing?
could you be yada-yadaing?
could they be yada-yadaing? 	could I have yada-yadaed?
could you have yada-yadaed?
could he have yada-yadaed?
could we have yada-yadaed?
could you have yada-yadaed?
could they have yada-yadaed? 	could I have been yada-yadaing?
could you have been yada-yadaing?
could he have been yada-yadaing?
could we have been yada-yadaing?
could you have been yada-yadaing?
could they have been yada-yadaing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not yada-yada?
could you not yada-yada?
could he not yada-yada?
could we not yada-yada?
could you not yada-yada?
could they not yada-yada? 	could I not be yada-yadaing?
could you not be yada-yadaing?
could he not be yada-yadaing?
could we not be yada-yadaing?
could you not be yada-yadaing?
could they not be yada-yadaing? 	could I not have yada-yadaed?
could you not have yada-yadaed?
could he not have yada-yadaed?
could we not have yada-yadaed?
could you not have yada-yadaed?
could they not have yada-yadaed? 	could I not have been yada-yadaing?
could you not have been yada-yadaing?
could he not have been yada-yadaing?
could we not have been yada-yadaing?
could you not have been yada-yadaing?
could they not have been yada-yadaing?