English verb conjugation
CAN LETTER

Regular verb: letter - lettered - lettered

Affirmation

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

Negation

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

Interrogative form

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

Interro-negative form

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