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
she must yack
we must yack
you must yack
they must yack 	I must be yacking
you must be yacking
she must be yacking
we must be yacking
you must be yacking
they must be yacking	I must have yacked
you must have yacked
she 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
she 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
she 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
she 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
she 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
she 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 she yack?
must we yack?
must you yack?
must they yack? 	must I be yacking?
must you be yacking?
must she be yacking?
must we be yacking?
must you be yacking?
must they be yacking? 	must I have yacked?
must you have yacked?
must she 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 she 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 she 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 she 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 she 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 she have been yacking?
mustn't we have been yacking?
mustn't you have been yacking?
mustn't they have been yacking?