must understand
Verbo irregular: understand - understood- understood

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I must understand
you must understand
he must understand
we must understand
you must understand
they must understand 	I must be understanding
you must be understanding
he must be understanding
we must be understanding
you must be understanding
they must be understanding	I must have understood
you must have understood
he must have understood
we must have understood
you must have understood
they must have understood	I must have been understanding
you must have been understanding
he must have been understanding
we must have been understanding
you must have been understanding
they must have been understanding	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I mustn't understand
you mustn't understand
he mustn't understand
we mustn't understand
you mustn't understand
they mustn't understand 	I mustn't be understanding
you mustn't be understanding
he mustn't be understanding
we mustn't be understanding
you mustn't be understanding
they mustn't be understanding	I mustn't have understood
you mustn't have understood
he mustn't have understood
we mustn't have understood
you mustn't have understood
they mustn't have understood	I mustn't have been understanding
you mustn't have been understanding
he mustn't have been understanding
we mustn't have been understanding
you mustn't have been understanding
they mustn't have been understanding	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
must I understand?
must you understand?
must he understand?
must we understand?
must you understand?
must they understand? 	must I be understanding?
must you be understanding?
must he be understanding?
must we be understanding?
must you be understanding?
must they be understanding? 	must I have understood?
must you have understood?
must he have understood?
must we have understood?
must you have understood?
must they have understood? 	must I have been understanding?
must you have been understanding?
must he have been understanding?
must we have been understanding?
must you have been understanding?
must they have been understanding? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
mustn't I understand?
mustn't you understand?
mustn't he understand?
mustn't we understand?
mustn't you understand?
mustn't they understand? 	mustn't I be understanding?
mustn't you be understanding?
mustn't he be understanding?
mustn't we be understanding?
mustn't you be understanding?
mustn't they be understanding? 	mustn't I have understood?
mustn't you have understood?
mustn't he have understood?
mustn't we have understood?
mustn't you have understood?
mustn't they have understood? 	mustn't I have been understanding?
mustn't you have been understanding?
mustn't he have been understanding?
mustn't we have been understanding?
mustn't you have been understanding?
mustn't they have been understanding?