must keen
Regular verb: keen - keened- keened

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must keen
you must keen
he must keen
we must keen
you must keen
they must keen 	I must be keening
you must be keening
he must be keening
we must be keening
you must be keening
they must be keening	I must have keened
you must have keened
he must have keened
we must have keened
you must have keened
they must have keened	I must have been keening
you must have been keening
he must have been keening
we must have been keening
you must have been keening
they must have been keening	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must not keen
you must not keen
he must not keen
we must not keen
you must not keen
they must not keen 	I must not be keening
you must not be keening
he must not be keening
we must not be keening
you must not be keening
they must not be keening	I must not have keened
you must not have keened
he must not have keened
we must not have keened
you must not have keened
they must not have keened	I must not have been keening
you must not have been keening
he must not have been keening
we must not have been keening
you must not have been keening
they must not have been keening	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I keen?
must you keen?
must he keen?
must we keen?
must you keen?
must they keen? 	must I be keening?
must you be keening?
must he be keening?
must we be keening?
must you be keening?
must they be keening? 	must I have keened?
must you have keened?
must he have keened?
must we have keened?
must you have keened?
must they have keened? 	must I have been keening?
must you have been keening?
must he have been keening?
must we have been keening?
must you have been keening?
must they have been keening? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I not keen?
must you not keen?
must he not keen?
must we not keen?
must you not keen?
must they not keen? 	must I not be keening?
must you not be keening?
must he not be keening?
must we not be keening?
must you not be keening?
must they not be keening? 	must I not have keened?
must you not have keened?
must he not have keened?
must we not have keened?
must you not have keened?
must they not have keened? 	must I not have been keening?
must you not have been keening?
must he not have been keening?
must we not have been keening?
must you not have been keening?
must they not have been keening?