English verb conjugation
MUST ERR

Regular verb: err - erred - erred

Affirmation

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

Negation

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

Interrogative form

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

Interro-negative form

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