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 must not stiffen
you must not stiffen
he must not stiffen
we must not stiffen
you must not stiffen
they must not stiffen

V-ing form

I must not be stiffening
you must not be stiffening
he must not be stiffening
we must not be stiffening
you must not be stiffening
they must not be stiffening

Perfect

I must not have stiffened
you must not have stiffened
he must not have stiffened
we must not have stiffened
you must not have stiffened
they must not have stiffened

V-ing perfect

I must not have been stiffening
you must not have been stiffening
he must not have been stiffening
we must not have been stiffening
you must not have been stiffening
they must not 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

must I not stiffen?
must you not stiffen?
must he not stiffen?
must we not stiffen?
must you not stiffen?
must they not stiffen?

V-ing form

must I not be stiffening?
must you not be stiffening?
must he not be stiffening?
must we not be stiffening?
must you not be stiffening?
must they not be stiffening?

Perfect

must I not have stiffened?
must you not have stiffened?
must he not have stiffened?
must we not have stiffened?
must you not have stiffened?
must they not have stiffened?

V-ing perfect

must I not have been stiffening?
must you not have been stiffening?
must he not have been stiffening?
must we not have been stiffening?
must you not have been stiffening?
must they not have been stiffening?

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