I must understand you must understand he must understand we must understand you must understand they must understand
V-ing form
I must be understanding you must be understanding he must be understanding we must be understanding you must be understanding they must be understanding
Perfect
I must have understood you must have understood he must have understood we must have understood you must have understood they must have understood
V-ing perfect
I must have been understanding you must have been understanding he must have been understanding we must have been understanding you must have been understanding they must have been understanding
Negation
Simple form
I must not understand you must not understand he must not understand we must not understand you must not understand they must not understand
V-ing form
I must not be understanding you must not be understanding he must not be understanding we must not be understanding you must not be understanding they must not be understanding
Perfect
I must not have understood you must not have understood he must not have understood we must not have understood you must not have understood they must not have understood
V-ing perfect
I must not have been understanding you must not have been understanding he must not have been understanding we must not have been understanding you must not have been understanding they must not have been understanding
Interrogative form
Simple form
must I understand? must you understand? must he understand? must we understand? must you understand? must they understand?
V-ing form
must I be understanding? must you be understanding? must he be understanding? must we be understanding? must you be understanding? must they be understanding?
Perfect
must I have understood? must you have understood? must he have understood? must we have understood? must you have understood? must they have understood?
V-ing perfect
must I have been understanding? must you have been understanding? must he have been understanding? must we have been understanding? must you have been understanding? must they have been understanding?
Interro-negative form
Simple form
must I not understand? must you not understand? must he not understand? must we not understand? must you not understand? must they not understand?
V-ing form
must I not be understanding? must you not be understanding? must he not be understanding? must we not be understanding? must you not be understanding? must they not be understanding?
Perfect
must I not have understood? must you not have understood? must he not have understood? must we not have understood? must you not have understood? must they not have understood?
V-ing perfect
must I not have been understanding? must you not have been understanding? must he not have been understanding? must we not have been understanding? must you not have been understanding? must they not have been understanding?