English verb conjugation
MUST BACKFIT

Irregular verb: backfit - backfit, backfitted - backfit, backfitted

Affirmation

Simple form	V-ing form
I must backfit you must backfit he must backfit we must backfit you must backfit they must backfit	I must be backfiting you must be backfiting he must be backfiting we must be backfiting you must be backfiting they must be backfiting
Perfect	V-ing perfect
I must have backfit, backfitted you must have backfit, backfitted he must have backfit, backfitted we must have backfit, backfitted you must have backfit, backfitted they must have backfit, backfitted	I must have been backfiting you must have been backfiting he must have been backfiting we must have been backfiting you must have been backfiting they must have been backfiting

Negation

Simple form	V-ing form
I mustn't backfit you mustn't backfit he mustn't backfit we mustn't backfit you mustn't backfit they mustn't backfit	I mustn't be backfiting you mustn't be backfiting he mustn't be backfiting we mustn't be backfiting you mustn't be backfiting they mustn't be backfiting
Perfect	V-ing perfect
I mustn't have backfit, backfitted you mustn't have backfit, backfitted he mustn't have backfit, backfitted we mustn't have backfit, backfitted you mustn't have backfit, backfitted they mustn't have backfit, backfitted	I mustn't have been backfiting you mustn't have been backfiting he mustn't have been backfiting we mustn't have been backfiting you mustn't have been backfiting they mustn't have been backfiting

Interrogative form

Simple form	V-ing form
must I backfit? must you backfit? must he backfit? must we backfit? must you backfit? must they backfit?	must I be backfiting? must you be backfiting? must he be backfiting? must we be backfiting? must you be backfiting? must they be backfiting?
Perfect	V-ing perfect
must I have backfit, backfitted? must you have backfit, backfitted? must he have backfit, backfitted? must we have backfit, backfitted? must you have backfit, backfitted? must they have backfit, backfitted?	must I have been backfiting? must you have been backfiting? must he have been backfiting? must we have been backfiting? must you have been backfiting? must they have been backfiting?

Interro-negative form

Simple form	V-ing form
mustn't I backfit? mustn't you backfit? mustn't he backfit? mustn't we backfit? mustn't you backfit? mustn't they backfit?	mustn't I be backfiting? mustn't you be backfiting? mustn't he be backfiting? mustn't we be backfiting? mustn't you be backfiting? mustn't they be backfiting?
Perfect	V-ing perfect
mustn't I have backfit, backfitted? mustn't you have backfit, backfitted? mustn't he have backfit, backfitted? mustn't we have backfit, backfitted? mustn't you have backfit, backfitted? mustn't they have backfit, backfitted?	mustn't I have been backfiting? mustn't you have been backfiting? mustn't he have been backfiting? mustn't we have been backfiting? mustn't you have been backfiting? mustn't they have been backfiting?