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 couldn't stiffen
you couldn't stiffen
he couldn't stiffen
we couldn't stiffen
you couldn't stiffen
they couldn't stiffen

V-ing form

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

Perfect

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

V-ing perfect

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

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

V-ing form

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

Perfect

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

V-ing perfect

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

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