must yak
Regular verb: yak - yaked- yaked

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must yak
you must yak
she must yak
we must yak
you must yak
they must yak 	I must be yaking
you must be yaking
she must be yaking
we must be yaking
you must be yaking
they must be yaking	I must have yaked
you must have yaked
she must have yaked
we must have yaked
you must have yaked
they must have yaked	I must have been yaking
you must have been yaking
she must have been yaking
we must have been yaking
you must have been yaking
they must have been yaking	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must not yak
you must not yak
she must not yak
we must not yak
you must not yak
they must not yak 	I must not be yaking
you must not be yaking
she must not be yaking
we must not be yaking
you must not be yaking
they must not be yaking	I must not have yaked
you must not have yaked
she must not have yaked
we must not have yaked
you must not have yaked
they must not have yaked	I must not have been yaking
you must not have been yaking
she must not have been yaking
we must not have been yaking
you must not have been yaking
they must not have been yaking	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I yak?
must you yak?
must she yak?
must we yak?
must you yak?
must they yak? 	must I be yaking?
must you be yaking?
must she be yaking?
must we be yaking?
must you be yaking?
must they be yaking? 	must I have yaked?
must you have yaked?
must she have yaked?
must we have yaked?
must you have yaked?
must they have yaked? 	must I have been yaking?
must you have been yaking?
must she have been yaking?
must we have been yaking?
must you have been yaking?
must they have been yaking? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I not yak?
must you not yak?
must she not yak?
must we not yak?
must you not yak?
must they not yak? 	must I not be yaking?
must you not be yaking?
must she not be yaking?
must we not be yaking?
must you not be yaking?
must they not be yaking? 	must I not have yaked?
must you not have yaked?
must she not have yaked?
must we not have yaked?
must you not have yaked?
must they not have yaked? 	must I not have been yaking?
must you not have been yaking?
must she not have been yaking?
must we not have been yaking?
must you not have been yaking?
must they not have been yaking?