English verb conjugation
MUST YAWN

Regular verb: yawn - yawned - yawned

Affirmation

Simple form	V-ing form
I must yawn you must yawn he must yawn we must yawn you must yawn they must yawn	I must be yawning you must be yawning he must be yawning we must be yawning you must be yawning they must be yawning
Perfect	V-ing perfect
I must have yawned you must have yawned he must have yawned we must have yawned you must have yawned they must have yawned	I must have been yawning you must have been yawning he must have been yawning we must have been yawning you must have been yawning they must have been yawning

Negation

Simple form	V-ing form
I mustn't yawn you mustn't yawn he mustn't yawn we mustn't yawn you mustn't yawn they mustn't yawn	I mustn't be yawning you mustn't be yawning he mustn't be yawning we mustn't be yawning you mustn't be yawning they mustn't be yawning
Perfect	V-ing perfect
I mustn't have yawned you mustn't have yawned he mustn't have yawned we mustn't have yawned you mustn't have yawned they mustn't have yawned	I mustn't have been yawning you mustn't have been yawning he mustn't have been yawning we mustn't have been yawning you mustn't have been yawning they mustn't have been yawning

Interrogative form

Simple form	V-ing form
must I yawn? must you yawn? must he yawn? must we yawn? must you yawn? must they yawn?	must I be yawning? must you be yawning? must he be yawning? must we be yawning? must you be yawning? must they be yawning?
Perfect	V-ing perfect
must I have yawned? must you have yawned? must he have yawned? must we have yawned? must you have yawned? must they have yawned?	must I have been yawning? must you have been yawning? must he have been yawning? must we have been yawning? must you have been yawning? must they have been yawning?

Interro-negative form

Simple form	V-ing form
mustn't I yawn? mustn't you yawn? mustn't he yawn? mustn't we yawn? mustn't you yawn? mustn't they yawn?	mustn't I be yawning? mustn't you be yawning? mustn't he be yawning? mustn't we be yawning? mustn't you be yawning? mustn't they be yawning?
Perfect	V-ing perfect
mustn't I have yawned? mustn't you have yawned? mustn't he have yawned? mustn't we have yawned? mustn't you have yawned? mustn't they have yawned?	mustn't I have been yawning? mustn't you have been yawning? mustn't he have been yawning? mustn't we have been yawning? mustn't you have been yawning? mustn't they have been yawning?