must decease
Regular verb: decease - deceased- deceased

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must decease
you must decease
he must decease
we must decease
you must decease
they must decease 	I must be deceasing
you must be deceasing
he must be deceasing
we must be deceasing
you must be deceasing
they must be deceasing	I must have deceased
you must have deceased
he must have deceased
we must have deceased
you must have deceased
they must have deceased	I must have been deceasing
you must have been deceasing
he must have been deceasing
we must have been deceasing
you must have been deceasing
they must have been deceasing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't decease
you mustn't decease
he mustn't decease
we mustn't decease
you mustn't decease
they mustn't decease 	I mustn't be deceasing
you mustn't be deceasing
he mustn't be deceasing
we mustn't be deceasing
you mustn't be deceasing
they mustn't be deceasing	I mustn't have deceased
you mustn't have deceased
he mustn't have deceased
we mustn't have deceased
you mustn't have deceased
they mustn't have deceased	I mustn't have been deceasing
you mustn't have been deceasing
he mustn't have been deceasing
we mustn't have been deceasing
you mustn't have been deceasing
they mustn't have been deceasing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I decease?
must you decease?
must he decease?
must we decease?
must you decease?
must they decease? 	must I be deceasing?
must you be deceasing?
must he be deceasing?
must we be deceasing?
must you be deceasing?
must they be deceasing? 	must I have deceased?
must you have deceased?
must he have deceased?
must we have deceased?
must you have deceased?
must they have deceased? 	must I have been deceasing?
must you have been deceasing?
must he have been deceasing?
must we have been deceasing?
must you have been deceasing?
must they have been deceasing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I decease?
mustn't you decease?
mustn't he decease?
mustn't we decease?
mustn't you decease?
mustn't they decease? 	mustn't I be deceasing?
mustn't you be deceasing?
mustn't he be deceasing?
mustn't we be deceasing?
mustn't you be deceasing?
mustn't they be deceasing? 	mustn't I have deceased?
mustn't you have deceased?
mustn't he have deceased?
mustn't we have deceased?
mustn't you have deceased?
mustn't they have deceased? 	mustn't I have been deceasing?
mustn't you have been deceasing?
mustn't he have been deceasing?
mustn't we have been deceasing?
mustn't you have been deceasing?
mustn't they have been deceasing?