must err
Verbe régulier : err - erred- erred
Traduction française : se tromper - pécher 

Affirmation 	
Forme simple 	Forme en V-ing 	Perfect 	Perfect en V-ing 	
I must err
you must err
he must err
we must err
you must err
they must err 	I must be erring
you must be erring
he must be erring
we must be erring
you must be erring
they must be erring	I must have erred
you must have erred
he 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
he must have been erring
we must have been erring
you must have been erring
they must have been erring	

Négation 	
Forme simple 	Forme en V-ing 	Perfect 	Perfect en V-ing 	
I mustn't err
you mustn't err
he 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
he mustn't be erring
we mustn't be erring
you mustn't be erring
they mustn't be erring	I mustn't have erred
you mustn't have erred
he 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
he mustn't have been erring
we mustn't have been erring
you mustn't have been erring
they mustn't have been erring	

Forme interrogative 	
Forme simple 	Forme en V-ing 	Perfect 	Perfect en V-ing 	
must I err?
must you err?
must he err?
must we err?
must you err?
must they err? 	must I be erring?
must you be erring?
must he be erring?
must we be erring?
must you be erring?
must they be erring? 	must I have erred?
must you have erred?
must he 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 he have been erring?
must we have been erring?
must you have been erring?
must they have been erring? 	

Forme interro-négative 	
Forme simple 	Forme en V-ing 	Perfect 	Perfect en V-ing 	
mustn't I err?
mustn't you err?
mustn't he 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 he be erring?
mustn't we be erring?
mustn't you be erring?
mustn't they be erring? 	mustn't I have erred?
mustn't you have erred?
mustn't he 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 he have been erring?
mustn't we have been erring?
mustn't you have been erring?
mustn't they have been erring?