English verb conjugation
MUST LENGTHEN

Regular verb: lengthen - lengthened - lengthened

Affirmation

Simple form	V-ing form
I must lengthen you must lengthen she must lengthen we must lengthen you must lengthen they must lengthen	I must be lengthening you must be lengthening she 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 she 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 she 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 she 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 she 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 she 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 she 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 she lengthen? must we lengthen? must you lengthen? must they lengthen?	must I be lengthening? must you be lengthening? must she 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 she 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 she 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 she 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 she 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 she 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 she have been lengthening? mustn't we have been lengthening? mustn't you have been lengthening? mustn't they have been lengthening?