could trephine
Regular verb: trephine - trephined- trephined

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could trephine
you could trephine
he could trephine
we could trephine
you could trephine
they could trephine 	I could be trephining
you could be trephining
he could be trephining
we could be trephining
you could be trephining
they could be trephining	I could have trephined
you could have trephined
he could have trephined
we could have trephined
you could have trephined
they could have trephined	I could have been trephining
you could have been trephining
he could have been trephining
we could have been trephining
you could have been trephining
they could have been trephining	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not trephine
you could not trephine
he could not trephine
we could not trephine
you could not trephine
they could not trephine 	I could not be trephining
you could not be trephining
he could not be trephining
we could not be trephining
you could not be trephining
they could not be trephining	I could not have trephined
you could not have trephined
he could not have trephined
we could not have trephined
you could not have trephined
they could not have trephined	I could not have been trephining
you could not have been trephining
he could not have been trephining
we could not have been trephining
you could not have been trephining
they could not have been trephining	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I trephine?
could you trephine?
could he trephine?
could we trephine?
could you trephine?
could they trephine? 	could I be trephining?
could you be trephining?
could he be trephining?
could we be trephining?
could you be trephining?
could they be trephining? 	could I have trephined?
could you have trephined?
could he have trephined?
could we have trephined?
could you have trephined?
could they have trephined? 	could I have been trephining?
could you have been trephining?
could he have been trephining?
could we have been trephining?
could you have been trephining?
could they have been trephining? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not trephine?
could you not trephine?
could he not trephine?
could we not trephine?
could you not trephine?
could they not trephine? 	could I not be trephining?
could you not be trephining?
could he not be trephining?
could we not be trephining?
could you not be trephining?
could they not be trephining? 	could I not have trephined?
could you not have trephined?
could he not have trephined?
could we not have trephined?
could you not have trephined?
could they not have trephined? 	could I not have been trephining?
could you not have been trephining?
could he not have been trephining?
could we not have been trephining?
could you not have been trephining?
could they not have been trephining?