English verb conjugation
MUST TIFF

Regular verb: tiff - tiffed - tiffed

Affirmation

Simple form	V-ing form
I must tiff you must tiff he must tiff we must tiff you must tiff they must tiff	I must be tiffing you must be tiffing he must be tiffing we must be tiffing you must be tiffing they must be tiffing
Perfect	V-ing perfect
I must have tiffed you must have tiffed he must have tiffed we must have tiffed you must have tiffed they must have tiffed	I must have been tiffing you must have been tiffing he must have been tiffing we must have been tiffing you must have been tiffing they must have been tiffing

Negation

Simple form	V-ing form
I must not tiff you must not tiff he must not tiff we must not tiff you must not tiff they must not tiff	I must not be tiffing you must not be tiffing he must not be tiffing we must not be tiffing you must not be tiffing they must not be tiffing
Perfect	V-ing perfect
I must not have tiffed you must not have tiffed he must not have tiffed we must not have tiffed you must not have tiffed they must not have tiffed	I must not have been tiffing you must not have been tiffing he must not have been tiffing we must not have been tiffing you must not have been tiffing they must not have been tiffing

Interrogative form

Simple form	V-ing form
must I tiff? must you tiff? must he tiff? must we tiff? must you tiff? must they tiff?	must I be tiffing? must you be tiffing? must he be tiffing? must we be tiffing? must you be tiffing? must they be tiffing?
Perfect	V-ing perfect
must I have tiffed? must you have tiffed? must he have tiffed? must we have tiffed? must you have tiffed? must they have tiffed?	must I have been tiffing? must you have been tiffing? must he have been tiffing? must we have been tiffing? must you have been tiffing? must they have been tiffing?

Interro-negative form

Simple form	V-ing form
must I not tiff? must you not tiff? must he not tiff? must we not tiff? must you not tiff? must they not tiff?	must I not be tiffing? must you not be tiffing? must he not be tiffing? must we not be tiffing? must you not be tiffing? must they not be tiffing?
Perfect	V-ing perfect
must I not have tiffed? must you not have tiffed? must he not have tiffed? must we not have tiffed? must you not have tiffed? must they not have tiffed?	must I not have been tiffing? must you not have been tiffing? must he not have been tiffing? must we not have been tiffing? must you not have been tiffing? must they not have been tiffing?