English verb conjugation
COULD HOWL

Regular verb: howl - howled - howled

Affirmation

Simple form	V-ing form
I could howl you could howl she could howl we could howl you could howl they could howl	I could be howling you could be howling she could be howling we could be howling you could be howling they could be howling
Perfect	V-ing perfect
I could have howled you could have howled she could have howled we could have howled you could have howled they could have howled	I could have been howling you could have been howling she could have been howling we could have been howling you could have been howling they could have been howling

Negation

Simple form	V-ing form
I couldn't howl you couldn't howl she couldn't howl we couldn't howl you couldn't howl they couldn't howl	I couldn't be howling you couldn't be howling she couldn't be howling we couldn't be howling you couldn't be howling they couldn't be howling
Perfect	V-ing perfect
I couldn't have howled you couldn't have howled she couldn't have howled we couldn't have howled you couldn't have howled they couldn't have howled	I couldn't have been howling you couldn't have been howling she couldn't have been howling we couldn't have been howling you couldn't have been howling they couldn't have been howling

Interrogative form

Simple form	V-ing form
could I howl? could you howl? could she howl? could we howl? could you howl? could they howl?	could I be howling? could you be howling? could she be howling? could we be howling? could you be howling? could they be howling?
Perfect	V-ing perfect
could I have howled? could you have howled? could she have howled? could we have howled? could you have howled? could they have howled?	could I have been howling? could you have been howling? could she have been howling? could we have been howling? could you have been howling? could they have been howling?

Interro-negative form

Simple form	V-ing form
couldn't I howl? couldn't you howl? couldn't she howl? couldn't we howl? couldn't you howl? couldn't they howl?	couldn't I be howling? couldn't you be howling? couldn't she be howling? couldn't we be howling? couldn't you be howling? couldn't they be howling?
Perfect	V-ing perfect
couldn't I have howled? couldn't you have howled? couldn't she have howled? couldn't we have howled? couldn't you have howled? couldn't they have howled?	couldn't I have been howling? couldn't you have been howling? couldn't she have been howling? couldn't we have been howling? couldn't you have been howling? couldn't they have been howling?