English verb conjugation
MUST YAWN

Regular verb: yawn - yawned - yawned

Affirmation

Simple form	V-ing form
I must yawn you must yawn she must yawn we must yawn you must yawn they must yawn	I must be yawning you must be yawning she 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 she 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 she 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 must not yawn you must not yawn she must not yawn we must not yawn you must not yawn they must not yawn	I must not be yawning you must not be yawning she must not be yawning we must not be yawning you must not be yawning they must not be yawning
Perfect	V-ing perfect
I must not have yawned you must not have yawned she must not have yawned we must not have yawned you must not have yawned they must not have yawned	I must not have been yawning you must not have been yawning she must not have been yawning we must not have been yawning you must not have been yawning they must not have been yawning

Interrogative form

Simple form	V-ing form
must I yawn? must you yawn? must she yawn? must we yawn? must you yawn? must they yawn?	must I be yawning? must you be yawning? must she 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 she 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 she 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
must I not yawn? must you not yawn? must she not yawn? must we not yawn? must you not yawn? must they not yawn?	must I not be yawning? must you not be yawning? must she not be yawning? must we not be yawning? must you not be yawning? must they not be yawning?
Perfect	V-ing perfect
must I not have yawned? must you not have yawned? must she not have yawned? must we not have yawned? must you not have yawned? must they not have yawned?	must I not have been yawning? must you not have been yawning? must she not have been yawning? must we not have been yawning? must you not have been yawning? must they not have been yawning?