English verb conjugation
COULD BILLOW

Regular verb: billow - billowed - billowed

Affirmation

Simple form	V-ing form
I could billow you could billow he could billow we could billow you could billow they could billow	I could be billowing you could be billowing he could be billowing we could be billowing you could be billowing they could be billowing
Perfect	V-ing perfect
I could have billowed you could have billowed he could have billowed we could have billowed you could have billowed they could have billowed	I could have been billowing you could have been billowing he could have been billowing we could have been billowing you could have been billowing they could have been billowing

Negation

Simple form	V-ing form
I could not billow you could not billow he could not billow we could not billow you could not billow they could not billow	I could not be billowing you could not be billowing he could not be billowing we could not be billowing you could not be billowing they could not be billowing
Perfect	V-ing perfect
I could not have billowed you could not have billowed he could not have billowed we could not have billowed you could not have billowed they could not have billowed	I could not have been billowing you could not have been billowing he could not have been billowing we could not have been billowing you could not have been billowing they could not have been billowing

Interrogative form

Simple form	V-ing form
could I billow? could you billow? could he billow? could we billow? could you billow? could they billow?	could I be billowing? could you be billowing? could he be billowing? could we be billowing? could you be billowing? could they be billowing?
Perfect	V-ing perfect
could I have billowed? could you have billowed? could he have billowed? could we have billowed? could you have billowed? could they have billowed?	could I have been billowing? could you have been billowing? could he have been billowing? could we have been billowing? could you have been billowing? could they have been billowing?

Interro-negative form

Simple form	V-ing form
could I not billow? could you not billow? could he not billow? could we not billow? could you not billow? could they not billow?	could I not be billowing? could you not be billowing? could he not be billowing? could we not be billowing? could you not be billowing? could they not be billowing?
Perfect	V-ing perfect
could I not have billowed? could you not have billowed? could he not have billowed? could we not have billowed? could you not have billowed? could they not have billowed?	could I not have been billowing? could you not have been billowing? could he not have been billowing? could we not have been billowing? could you not have been billowing? could they not have been billowing?