English verb conjugation
COULD ERR

Regular verb: err - erred - erred

Affirmation

Simple form	V-ing form
I could err you could err she could err we could err you could err they could err	I could be erring you could be erring she could be erring we could be erring you could be erring they could be erring
Perfect	V-ing perfect
I could have erred you could have erred she could have erred we could have erred you could have erred they could have erred	I could have been erring you could have been erring she could have been erring we could have been erring you could have been erring they could have been erring

Negation

Simple form	V-ing form
I couldn't err you couldn't err she couldn't err we couldn't err you couldn't err they couldn't err	I couldn't be erring you couldn't be erring she couldn't be erring we couldn't be erring you couldn't be erring they couldn't be erring
Perfect	V-ing perfect
I couldn't have erred you couldn't have erred she couldn't have erred we couldn't have erred you couldn't have erred they couldn't have erred	I couldn't have been erring you couldn't have been erring she couldn't have been erring we couldn't have been erring you couldn't have been erring they couldn't have been erring

Interrogative form

Simple form	V-ing form
could I err? could you err? could she err? could we err? could you err? could they err?	could I be erring? could you be erring? could she be erring? could we be erring? could you be erring? could they be erring?
Perfect	V-ing perfect
could I have erred? could you have erred? could she have erred? could we have erred? could you have erred? could they have erred?	could I have been erring? could you have been erring? could she have been erring? could we have been erring? could you have been erring? could they have been erring?

Interro-negative form

Simple form	V-ing form
couldn't I err? couldn't you err? couldn't she err? couldn't we err? couldn't you err? couldn't they err?	couldn't I be erring? couldn't you be erring? couldn't she be erring? couldn't we be erring? couldn't you be erring? couldn't they be erring?
Perfect	V-ing perfect
couldn't I have erred? couldn't you have erred? couldn't she have erred? couldn't we have erred? couldn't you have erred? couldn't they have erred?	couldn't I have been erring? couldn't you have been erring? couldn't she have been erring? couldn't we have been erring? couldn't you have been erring? couldn't they have been erring?