could unnail
Regular verb: unnail - unnailed- unnailed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could unnail
you could unnail
he could unnail
we could unnail
you could unnail
they could unnail 	I could be unnailing
you could be unnailing
he could be unnailing
we could be unnailing
you could be unnailing
they could be unnailing	I could have unnailed
you could have unnailed
he could have unnailed
we could have unnailed
you could have unnailed
they could have unnailed	I could have been unnailing
you could have been unnailing
he could have been unnailing
we could have been unnailing
you could have been unnailing
they could have been unnailing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't unnail
you couldn't unnail
he couldn't unnail
we couldn't unnail
you couldn't unnail
they couldn't unnail 	I couldn't be unnailing
you couldn't be unnailing
he couldn't be unnailing
we couldn't be unnailing
you couldn't be unnailing
they couldn't be unnailing	I couldn't have unnailed
you couldn't have unnailed
he couldn't have unnailed
we couldn't have unnailed
you couldn't have unnailed
they couldn't have unnailed	I couldn't have been unnailing
you couldn't have been unnailing
he couldn't have been unnailing
we couldn't have been unnailing
you couldn't have been unnailing
they couldn't have been unnailing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I unnail?
could you unnail?
could he unnail?
could we unnail?
could you unnail?
could they unnail? 	could I be unnailing?
could you be unnailing?
could he be unnailing?
could we be unnailing?
could you be unnailing?
could they be unnailing? 	could I have unnailed?
could you have unnailed?
could he have unnailed?
could we have unnailed?
could you have unnailed?
could they have unnailed? 	could I have been unnailing?
could you have been unnailing?
could he have been unnailing?
could we have been unnailing?
could you have been unnailing?
could they have been unnailing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I unnail?
couldn't you unnail?
couldn't he unnail?
couldn't we unnail?
couldn't you unnail?
couldn't they unnail? 	couldn't I be unnailing?
couldn't you be unnailing?
couldn't he be unnailing?
couldn't we be unnailing?
couldn't you be unnailing?
couldn't they be unnailing? 	couldn't I have unnailed?
couldn't you have unnailed?
couldn't he have unnailed?
couldn't we have unnailed?
couldn't you have unnailed?
couldn't they have unnailed? 	couldn't I have been unnailing?
couldn't you have been unnailing?
couldn't he have been unnailing?
couldn't we have been unnailing?
couldn't you have been unnailing?
couldn't they have been unnailing?