English verb conjugation
MUST LENGTHEN

Regular verb: lengthen - lengthened - lengthened

Affirmation

Simple form	V-ing form
I must lengthen you must lengthen he must lengthen we must lengthen you must lengthen they must lengthen	I must be lengthening you must be lengthening he must be lengthening we must be lengthening you must be lengthening they must be lengthening
Perfect	V-ing perfect
I must have lengthened you must have lengthened he must have lengthened we must have lengthened you must have lengthened they must have lengthened	I must have been lengthening you must have been lengthening he must have been lengthening we must have been lengthening you must have been lengthening they must have been lengthening

Negation

Simple form	V-ing form
I mustn't lengthen you mustn't lengthen he mustn't lengthen we mustn't lengthen you mustn't lengthen they mustn't lengthen	I mustn't be lengthening you mustn't be lengthening he mustn't be lengthening we mustn't be lengthening you mustn't be lengthening they mustn't be lengthening
Perfect	V-ing perfect
I mustn't have lengthened you mustn't have lengthened he mustn't have lengthened we mustn't have lengthened you mustn't have lengthened they mustn't have lengthened	I mustn't have been lengthening you mustn't have been lengthening he mustn't have been lengthening we mustn't have been lengthening you mustn't have been lengthening they mustn't have been lengthening

Interrogative form

Simple form	V-ing form
must I lengthen? must you lengthen? must he lengthen? must we lengthen? must you lengthen? must they lengthen?	must I be lengthening? must you be lengthening? must he be lengthening? must we be lengthening? must you be lengthening? must they be lengthening?
Perfect	V-ing perfect
must I have lengthened? must you have lengthened? must he have lengthened? must we have lengthened? must you have lengthened? must they have lengthened?	must I have been lengthening? must you have been lengthening? must he have been lengthening? must we have been lengthening? must you have been lengthening? must they have been lengthening?

Interro-negative form

Simple form	V-ing form
mustn't I lengthen? mustn't you lengthen? mustn't he lengthen? mustn't we lengthen? mustn't you lengthen? mustn't they lengthen?	mustn't I be lengthening? mustn't you be lengthening? mustn't he be lengthening? mustn't we be lengthening? mustn't you be lengthening? mustn't they be lengthening?
Perfect	V-ing perfect
mustn't I have lengthened? mustn't you have lengthened? mustn't he have lengthened? mustn't we have lengthened? mustn't you have lengthened? mustn't they have lengthened?	mustn't I have been lengthening? mustn't you have been lengthening? mustn't he have been lengthening? mustn't we have been lengthening? mustn't you have been lengthening? mustn't they have been lengthening?