English verb conjugation
COULD LETTER

Regular verb: letter - lettered - lettered

Affirmation

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

Negation

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

Interrogative form

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

Interro-negative form

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