could letter letter
Regular verb: letter letter - letter lettered- letter lettered

, this verb may not exist. Conjugation is given as example.

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could letter letter
you could letter letter
she could letter letter
we could letter letter
you could letter letter
they could letter letter 	I could be letter lettering
you could be letter lettering
she could be letter lettering
we could be letter lettering
you could be letter lettering
they could be letter lettering	I could have letter lettered
you could have letter lettered
she could have letter lettered
we could have letter lettered
you could have letter lettered
they could have letter lettered	I could have been letter lettering
you could have been letter lettering
she could have been letter lettering
we could have been letter lettering
you could have been letter lettering
they could have been letter lettering	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not letter letter
you could not letter letter
she could not letter letter
we could not letter letter
you could not letter letter
they could not letter letter 	I could not be letter lettering
you could not be letter lettering
she could not be letter lettering
we could not be letter lettering
you could not be letter lettering
they could not be letter lettering	I could not have letter lettered
you could not have letter lettered
she could not have letter lettered
we could not have letter lettered
you could not have letter lettered
they could not have letter lettered	I could not have been letter lettering
you could not have been letter lettering
she could not have been letter lettering
we could not have been letter lettering
you could not have been letter lettering
they could not have been letter lettering	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I letter letter?
could you letter letter?
could she letter letter?
could we letter letter?
could you letter letter?
could they letter letter? 	could I be letter lettering?
could you be letter lettering?
could she be letter lettering?
could we be letter lettering?
could you be letter lettering?
could they be letter lettering? 	could I have letter lettered?
could you have letter lettered?
could she have letter lettered?
could we have letter lettered?
could you have letter lettered?
could they have letter lettered? 	could I have been letter lettering?
could you have been letter lettering?
could she have been letter lettering?
could we have been letter lettering?
could you have been letter lettering?
could they have been letter lettering? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not letter letter?
could you not letter letter?
could she not letter letter?
could we not letter letter?
could you not letter letter?
could they not letter letter? 	could I not be letter lettering?
could you not be letter lettering?
could she not be letter lettering?
could we not be letter lettering?
could you not be letter lettering?
could they not be letter lettering? 	could I not have letter lettered?
could you not have letter lettered?
could she not have letter lettered?
could we not have letter lettered?
could you not have letter lettered?
could they not have letter lettered? 	could I not have been letter lettering?
could you not have been letter lettering?
could she not have been letter lettering?
could we not have been letter lettering?
could you not have been letter lettering?
could they not have been letter lettering?