English verb conjugation
MUST SPIFF

Regular verb: spiff - spiffed - spiffed

Affirmation

Simple form	V-ing form
I must spiff you must spiff he must spiff we must spiff you must spiff they must spiff	I must be spiffing you must be spiffing he must be spiffing we must be spiffing you must be spiffing they must be spiffing
Perfect	V-ing perfect
I must have spiffed you must have spiffed he must have spiffed we must have spiffed you must have spiffed they must have spiffed	I must have been spiffing you must have been spiffing he must have been spiffing we must have been spiffing you must have been spiffing they must have been spiffing

Negation

Simple form	V-ing form
I mustn't spiff you mustn't spiff he mustn't spiff we mustn't spiff you mustn't spiff they mustn't spiff	I mustn't be spiffing you mustn't be spiffing he mustn't be spiffing we mustn't be spiffing you mustn't be spiffing they mustn't be spiffing
Perfect	V-ing perfect
I mustn't have spiffed you mustn't have spiffed he mustn't have spiffed we mustn't have spiffed you mustn't have spiffed they mustn't have spiffed	I mustn't have been spiffing you mustn't have been spiffing he mustn't have been spiffing we mustn't have been spiffing you mustn't have been spiffing they mustn't have been spiffing

Interrogative form

Simple form	V-ing form
must I spiff? must you spiff? must he spiff? must we spiff? must you spiff? must they spiff?	must I be spiffing? must you be spiffing? must he be spiffing? must we be spiffing? must you be spiffing? must they be spiffing?
Perfect	V-ing perfect
must I have spiffed? must you have spiffed? must he have spiffed? must we have spiffed? must you have spiffed? must they have spiffed?	must I have been spiffing? must you have been spiffing? must he have been spiffing? must we have been spiffing? must you have been spiffing? must they have been spiffing?

Interro-negative form

Simple form	V-ing form
mustn't I spiff? mustn't you spiff? mustn't he spiff? mustn't we spiff? mustn't you spiff? mustn't they spiff?	mustn't I be spiffing? mustn't you be spiffing? mustn't he be spiffing? mustn't we be spiffing? mustn't you be spiffing? mustn't they be spiffing?
Perfect	V-ing perfect
mustn't I have spiffed? mustn't you have spiffed? mustn't he have spiffed? mustn't we have spiffed? mustn't you have spiffed? mustn't they have spiffed?	mustn't I have been spiffing? mustn't you have been spiffing? mustn't he have been spiffing? mustn't we have been spiffing? mustn't you have been spiffing? mustn't they have been spiffing?