must yack
Verbe régulier : yack - yacked- yacked

Affirmation 	
Forme simple 	Forme en V-ing 	Perfect 	Perfect en V-ing 	
I must yack
you must yack
he must yack
we must yack
you must yack
they must yack 	I must be yacking
you must be yacking
he must be yacking
we must be yacking
you must be yacking
they must be yacking	I must have yacked
you must have yacked
he must have yacked
we must have yacked
you must have yacked
they must have yacked	I must have been yacking
you must have been yacking
he must have been yacking
we must have been yacking
you must have been yacking
they must have been yacking	

Négation 	
Forme simple 	Forme en V-ing 	Perfect 	Perfect en V-ing 	
I mustn't yack
you mustn't yack
he mustn't yack
we mustn't yack
you mustn't yack
they mustn't yack 	I mustn't be yacking
you mustn't be yacking
he mustn't be yacking
we mustn't be yacking
you mustn't be yacking
they mustn't be yacking	I mustn't have yacked
you mustn't have yacked
he mustn't have yacked
we mustn't have yacked
you mustn't have yacked
they mustn't have yacked	I mustn't have been yacking
you mustn't have been yacking
he mustn't have been yacking
we mustn't have been yacking
you mustn't have been yacking
they mustn't have been yacking	

Forme interrogative 	
Forme simple 	Forme en V-ing 	Perfect 	Perfect en V-ing 	
must I yack?
must you yack?
must he yack?
must we yack?
must you yack?
must they yack? 	must I be yacking?
must you be yacking?
must he be yacking?
must we be yacking?
must you be yacking?
must they be yacking? 	must I have yacked?
must you have yacked?
must he have yacked?
must we have yacked?
must you have yacked?
must they have yacked? 	must I have been yacking?
must you have been yacking?
must he have been yacking?
must we have been yacking?
must you have been yacking?
must they have been yacking? 	

Forme interro-négative 	
Forme simple 	Forme en V-ing 	Perfect 	Perfect en V-ing 	
mustn't I yack?
mustn't you yack?
mustn't he yack?
mustn't we yack?
mustn't you yack?
mustn't they yack? 	mustn't I be yacking?
mustn't you be yacking?
mustn't he be yacking?
mustn't we be yacking?
mustn't you be yacking?
mustn't they be yacking? 	mustn't I have yacked?
mustn't you have yacked?
mustn't he have yacked?
mustn't we have yacked?
mustn't you have yacked?
mustn't they have yacked? 	mustn't I have been yacking?
mustn't you have been yacking?
mustn't he have been yacking?
mustn't we have been yacking?
mustn't you have been yacking?
mustn't they have been yacking?