must buy
Irregular verb: buy - bought- bought

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must buy
you must buy
he must buy
we must buy
you must buy
they must buy 	I must be buying
you must be buying
he must be buying
we must be buying
you must be buying
they must be buying	I must have bought
you must have bought
he must have bought
we must have bought
you must have bought
they must have bought	I must have been buying
you must have been buying
he must have been buying
we must have been buying
you must have been buying
they must have been buying	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't buy
you mustn't buy
he mustn't buy
we mustn't buy
you mustn't buy
they mustn't buy 	I mustn't be buying
you mustn't be buying
he mustn't be buying
we mustn't be buying
you mustn't be buying
they mustn't be buying	I mustn't have bought
you mustn't have bought
he mustn't have bought
we mustn't have bought
you mustn't have bought
they mustn't have bought	I mustn't have been buying
you mustn't have been buying
he mustn't have been buying
we mustn't have been buying
you mustn't have been buying
they mustn't have been buying	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I buy?
must you buy?
must he buy?
must we buy?
must you buy?
must they buy? 	must I be buying?
must you be buying?
must he be buying?
must we be buying?
must you be buying?
must they be buying? 	must I have bought?
must you have bought?
must he have bought?
must we have bought?
must you have bought?
must they have bought? 	must I have been buying?
must you have been buying?
must he have been buying?
must we have been buying?
must you have been buying?
must they have been buying? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I buy?
mustn't you buy?
mustn't he buy?
mustn't we buy?
mustn't you buy?
mustn't they buy? 	mustn't I be buying?
mustn't you be buying?
mustn't he be buying?
mustn't we be buying?
mustn't you be buying?
mustn't they be buying? 	mustn't I have bought?
mustn't you have bought?
mustn't he have bought?
mustn't we have bought?
mustn't you have bought?
mustn't they have bought? 	mustn't I have been buying?
mustn't you have been buying?
mustn't he have been buying?
mustn't we have been buying?
mustn't you have been buying?
mustn't they have been buying?