could thread
Regular verb: thread - threaded- threaded

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could thread
you could thread
she could thread
we could thread
you could thread
they could thread 	I could be threading
you could be threading
she could be threading
we could be threading
you could be threading
they could be threading	I could have threaded
you could have threaded
she could have threaded
we could have threaded
you could have threaded
they could have threaded	I could have been threading
you could have been threading
she could have been threading
we could have been threading
you could have been threading
they could have been threading	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not thread
you could not thread
she could not thread
we could not thread
you could not thread
they could not thread 	I could not be threading
you could not be threading
she could not be threading
we could not be threading
you could not be threading
they could not be threading	I could not have threaded
you could not have threaded
she could not have threaded
we could not have threaded
you could not have threaded
they could not have threaded	I could not have been threading
you could not have been threading
she could not have been threading
we could not have been threading
you could not have been threading
they could not have been threading	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I thread?
could you thread?
could she thread?
could we thread?
could you thread?
could they thread? 	could I be threading?
could you be threading?
could she be threading?
could we be threading?
could you be threading?
could they be threading? 	could I have threaded?
could you have threaded?
could she have threaded?
could we have threaded?
could you have threaded?
could they have threaded? 	could I have been threading?
could you have been threading?
could she have been threading?
could we have been threading?
could you have been threading?
could they have been threading? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not thread?
could you not thread?
could she not thread?
could we not thread?
could you not thread?
could they not thread? 	could I not be threading?
could you not be threading?
could she not be threading?
could we not be threading?
could you not be threading?
could they not be threading? 	could I not have threaded?
could you not have threaded?
could she not have threaded?
could we not have threaded?
could you not have threaded?
could they not have threaded? 	could I not have been threading?
could you not have been threading?
could she not have been threading?
could we not have been threading?
could you not have been threading?
could they not have been threading?