English verb conjugation COULD STIFFEN

Regular verb: stiffen - stiffened - stiffened

Affirmation

Simple form

I could stiffen
you could stiffen
he could stiffen
we could stiffen
you could stiffen
they could stiffen

V-ing form

I could be stiffening
you could be stiffening
he could be stiffening
we could be stiffening
you could be stiffening
they could be stiffening

Perfect

I could have stiffened
you could have stiffened
he could have stiffened
we could have stiffened
you could have stiffened
they could have stiffened

V-ing perfect

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

Negation

Simple form

I could not stiffen
you could not stiffen
he could not stiffen
we could not stiffen
you could not stiffen
they could not stiffen

V-ing form

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

Perfect

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

V-ing perfect

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

Interrogative form

Simple form

could I stiffen?
could you stiffen?
could he stiffen?
could we stiffen?
could you stiffen?
could they stiffen?

V-ing form

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

Perfect

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

V-ing perfect

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

Interro-negative form

Simple form

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

V-ing form

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

Perfect

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

V-ing perfect

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

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