could tinker
Regular verb: tinker - tinkered- tinkered

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could tinker
you could tinker
she could tinker
we could tinker
you could tinker
they could tinker 	I could be tinkering
you could be tinkering
she could be tinkering
we could be tinkering
you could be tinkering
they could be tinkering	I could have tinkered
you could have tinkered
she could have tinkered
we could have tinkered
you could have tinkered
they could have tinkered	I could have been tinkering
you could have been tinkering
she could have been tinkering
we could have been tinkering
you could have been tinkering
they could have been tinkering	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not tinker
you could not tinker
she could not tinker
we could not tinker
you could not tinker
they could not tinker 	I could not be tinkering
you could not be tinkering
she could not be tinkering
we could not be tinkering
you could not be tinkering
they could not be tinkering	I could not have tinkered
you could not have tinkered
she could not have tinkered
we could not have tinkered
you could not have tinkered
they could not have tinkered	I could not have been tinkering
you could not have been tinkering
she could not have been tinkering
we could not have been tinkering
you could not have been tinkering
they could not have been tinkering	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I tinker?
could you tinker?
could she tinker?
could we tinker?
could you tinker?
could they tinker? 	could I be tinkering?
could you be tinkering?
could she be tinkering?
could we be tinkering?
could you be tinkering?
could they be tinkering? 	could I have tinkered?
could you have tinkered?
could she have tinkered?
could we have tinkered?
could you have tinkered?
could they have tinkered? 	could I have been tinkering?
could you have been tinkering?
could she have been tinkering?
could we have been tinkering?
could you have been tinkering?
could they have been tinkering? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not tinker?
could you not tinker?
could she not tinker?
could we not tinker?
could you not tinker?
could they not tinker? 	could I not be tinkering?
could you not be tinkering?
could she not be tinkering?
could we not be tinkering?
could you not be tinkering?
could they not be tinkering? 	could I not have tinkered?
could you not have tinkered?
could she not have tinkered?
could we not have tinkered?
could you not have tinkered?
could they not have tinkered? 	could I not have been tinkering?
could you not have been tinkering?
could she not have been tinkering?
could we not have been tinkering?
could you not have been tinkering?
could they not have been tinkering?