must grin
Regular verb: grin - grinned- grinned

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must grin
you must grin
he must grin
we must grin
you must grin
they must grin 	I must be grinning
you must be grinning
he must be grinning
we must be grinning
you must be grinning
they must be grinning	I must have grinned
you must have grinned
he must have grinned
we must have grinned
you must have grinned
they must have grinned	I must have been grinning
you must have been grinning
he must have been grinning
we must have been grinning
you must have been grinning
they must have been grinning	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't grin
you mustn't grin
he mustn't grin
we mustn't grin
you mustn't grin
they mustn't grin 	I mustn't be grinning
you mustn't be grinning
he mustn't be grinning
we mustn't be grinning
you mustn't be grinning
they mustn't be grinning	I mustn't have grinned
you mustn't have grinned
he mustn't have grinned
we mustn't have grinned
you mustn't have grinned
they mustn't have grinned	I mustn't have been grinning
you mustn't have been grinning
he mustn't have been grinning
we mustn't have been grinning
you mustn't have been grinning
they mustn't have been grinning	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I grin?
must you grin?
must he grin?
must we grin?
must you grin?
must they grin? 	must I be grinning?
must you be grinning?
must he be grinning?
must we be grinning?
must you be grinning?
must they be grinning? 	must I have grinned?
must you have grinned?
must he have grinned?
must we have grinned?
must you have grinned?
must they have grinned? 	must I have been grinning?
must you have been grinning?
must he have been grinning?
must we have been grinning?
must you have been grinning?
must they have been grinning? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I grin?
mustn't you grin?
mustn't he grin?
mustn't we grin?
mustn't you grin?
mustn't they grin? 	mustn't I be grinning?
mustn't you be grinning?
mustn't he be grinning?
mustn't we be grinning?
mustn't you be grinning?
mustn't they be grinning? 	mustn't I have grinned?
mustn't you have grinned?
mustn't he have grinned?
mustn't we have grinned?
mustn't you have grinned?
mustn't they have grinned? 	mustn't I have been grinning?
mustn't you have been grinning?
mustn't he have been grinning?
mustn't we have been grinning?
mustn't you have been grinning?
mustn't they have been grinning?