English verb conjugation MUST STIFFEN

Regular verb: stiffen - stiffened - stiffened

Affirmation

Simple form

I must stiffen
you must stiffen
he must stiffen
we must stiffen
you must stiffen
they must stiffen

V-ing form

I must be stiffening
you must be stiffening
he must be stiffening
we must be stiffening
you must be stiffening
they must be stiffening

Perfect

I must have stiffened
you must have stiffened
he must have stiffened
we must have stiffened
you must have stiffened
they must have stiffened

V-ing perfect

I must have been stiffening
you must have been stiffening
he must have been stiffening
we must have been stiffening
you must have been stiffening
they must have been stiffening

Negation

Simple form

I mustn't stiffen
you mustn't stiffen
he mustn't stiffen
we mustn't stiffen
you mustn't stiffen
they mustn't stiffen

V-ing form

I mustn't be stiffening
you mustn't be stiffening
he mustn't be stiffening
we mustn't be stiffening
you mustn't be stiffening
they mustn't be stiffening

Perfect

I mustn't have stiffened
you mustn't have stiffened
he mustn't have stiffened
we mustn't have stiffened
you mustn't have stiffened
they mustn't have stiffened

V-ing perfect

I mustn't have been stiffening
you mustn't have been stiffening
he mustn't have been stiffening
we mustn't have been stiffening
you mustn't have been stiffening
they mustn't have been stiffening

Interrogative form

Simple form

must I stiffen?
must you stiffen?
must he stiffen?
must we stiffen?
must you stiffen?
must they stiffen?

V-ing form

must I be stiffening?
must you be stiffening?
must he be stiffening?
must we be stiffening?
must you be stiffening?
must they be stiffening?

Perfect

must I have stiffened?
must you have stiffened?
must he have stiffened?
must we have stiffened?
must you have stiffened?
must they have stiffened?

V-ing perfect

must I have been stiffening?
must you have been stiffening?
must he have been stiffening?
must we have been stiffening?
must you have been stiffening?
must they have been stiffening?

Interro-negative form

Simple form

mustn't I stiffen?
mustn't you stiffen?
mustn't he stiffen?
mustn't we stiffen?
mustn't you stiffen?
mustn't they stiffen?

V-ing form

mustn't I be stiffening?
mustn't you be stiffening?
mustn't he be stiffening?
mustn't we be stiffening?
mustn't you be stiffening?
mustn't they be stiffening?

Perfect

mustn't I have stiffened?
mustn't you have stiffened?
mustn't he have stiffened?
mustn't we have stiffened?
mustn't you have stiffened?
mustn't they have stiffened?

V-ing perfect

mustn't I have been stiffening?
mustn't you have been stiffening?
mustn't he have been stiffening?
mustn't we have been stiffening?
mustn't you have been stiffening?
mustn't they have been stiffening?

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