English verb conjugation
COULD HEIGHTEN

Regular verb: heighten - heightened - heightened

Affirmation

Simple form	V-ing form
I could heighten you could heighten he could heighten we could heighten you could heighten they could heighten	I could be heightening you could be heightening he could be heightening we could be heightening you could be heightening they could be heightening
Perfect	V-ing perfect
I could have heightened you could have heightened he could have heightened we could have heightened you could have heightened they could have heightened	I could have been heightening you could have been heightening he could have been heightening we could have been heightening you could have been heightening they could have been heightening

Negation

Simple form	V-ing form
I couldn't heighten you couldn't heighten he couldn't heighten we couldn't heighten you couldn't heighten they couldn't heighten	I couldn't be heightening you couldn't be heightening he couldn't be heightening we couldn't be heightening you couldn't be heightening they couldn't be heightening
Perfect	V-ing perfect
I couldn't have heightened you couldn't have heightened he couldn't have heightened we couldn't have heightened you couldn't have heightened they couldn't have heightened	I couldn't have been heightening you couldn't have been heightening he couldn't have been heightening we couldn't have been heightening you couldn't have been heightening they couldn't have been heightening

Interrogative form

Simple form	V-ing form
could I heighten? could you heighten? could he heighten? could we heighten? could you heighten? could they heighten?	could I be heightening? could you be heightening? could he be heightening? could we be heightening? could you be heightening? could they be heightening?
Perfect	V-ing perfect
could I have heightened? could you have heightened? could he have heightened? could we have heightened? could you have heightened? could they have heightened?	could I have been heightening? could you have been heightening? could he have been heightening? could we have been heightening? could you have been heightening? could they have been heightening?

Interro-negative form

Simple form	V-ing form
couldn't I heighten? couldn't you heighten? couldn't he heighten? couldn't we heighten? couldn't you heighten? couldn't they heighten?	couldn't I be heightening? couldn't you be heightening? couldn't he be heightening? couldn't we be heightening? couldn't you be heightening? couldn't they be heightening?
Perfect	V-ing perfect
couldn't I have heightened? couldn't you have heightened? couldn't he have heightened? couldn't we have heightened? couldn't you have heightened? couldn't they have heightened?	couldn't I have been heightening? couldn't you have been heightening? couldn't he have been heightening? couldn't we have been heightening? couldn't you have been heightening? couldn't they have been heightening?