Warning, this verb may not exist. Conjugation is given as example.
Affirmation
Simple form
I must lack lack you must lack lack he must lack lack we must lack lack you must lack lack they must lack lack
V-ing form
I must be lack lacking you must be lack lacking he must be lack lacking we must be lack lacking you must be lack lacking they must be lack lacking
Perfect
I must have lack lacked you must have lack lacked he must have lack lacked we must have lack lacked you must have lack lacked they must have lack lacked
V-ing perfect
I must have been lack lacking you must have been lack lacking he must have been lack lacking we must have been lack lacking you must have been lack lacking they must have been lack lacking
Negation
Simple form
I must not lack lack you must not lack lack he must not lack lack we must not lack lack you must not lack lack they must not lack lack
V-ing form
I must not be lack lacking you must not be lack lacking he must not be lack lacking we must not be lack lacking you must not be lack lacking they must not be lack lacking
Perfect
I must not have lack lacked you must not have lack lacked he must not have lack lacked we must not have lack lacked you must not have lack lacked they must not have lack lacked
V-ing perfect
I must not have been lack lacking you must not have been lack lacking he must not have been lack lacking we must not have been lack lacking you must not have been lack lacking they must not have been lack lacking
Interrogative form
Simple form
must I lack lack? must you lack lack? must he lack lack? must we lack lack? must you lack lack? must they lack lack?
V-ing form
must I be lack lacking? must you be lack lacking? must he be lack lacking? must we be lack lacking? must you be lack lacking? must they be lack lacking?
Perfect
must I have lack lacked? must you have lack lacked? must he have lack lacked? must we have lack lacked? must you have lack lacked? must they have lack lacked?
V-ing perfect
must I have been lack lacking? must you have been lack lacking? must he have been lack lacking? must we have been lack lacking? must you have been lack lacking? must they have been lack lacking?
Interro-negative form
Simple form
must I not lack lack? must you not lack lack? must he not lack lack? must we not lack lack? must you not lack lack? must they not lack lack?
V-ing form
must I not be lack lacking? must you not be lack lacking? must he not be lack lacking? must we not be lack lacking? must you not be lack lacking? must they not be lack lacking?
Perfect
must I not have lack lacked? must you not have lack lacked? must he not have lack lacked? must we not have lack lacked? must you not have lack lacked? must they not have lack lacked?
V-ing perfect
must I not have been lack lacking? must you not have been lack lacking? must he not have been lack lacking? must we not have been lack lacking? must you not have been lack lacking? must they not have been lack lacking?