English verb conjugation
COULD WINDOW

Regular verb: window - windowed - windowed

Affirmation

Simple form	V-ing form
I could window you could window he could window we could window you could window they could window	I could be windowing you could be windowing he could be windowing we could be windowing you could be windowing they could be windowing
Perfect	V-ing perfect
I could have windowed you could have windowed he could have windowed we could have windowed you could have windowed they could have windowed	I could have been windowing you could have been windowing he could have been windowing we could have been windowing you could have been windowing they could have been windowing

Negation

Simple form	V-ing form
I could not window you could not window he could not window we could not window you could not window they could not window	I could not be windowing you could not be windowing he could not be windowing we could not be windowing you could not be windowing they could not be windowing
Perfect	V-ing perfect
I could not have windowed you could not have windowed he could not have windowed we could not have windowed you could not have windowed they could not have windowed	I could not have been windowing you could not have been windowing he could not have been windowing we could not have been windowing you could not have been windowing they could not have been windowing

Interrogative form

Simple form	V-ing form
could I window? could you window? could he window? could we window? could you window? could they window?	could I be windowing? could you be windowing? could he be windowing? could we be windowing? could you be windowing? could they be windowing?
Perfect	V-ing perfect
could I have windowed? could you have windowed? could he have windowed? could we have windowed? could you have windowed? could they have windowed?	could I have been windowing? could you have been windowing? could he have been windowing? could we have been windowing? could you have been windowing? could they have been windowing?

Interro-negative form

Simple form	V-ing form
could I not window? could you not window? could he not window? could we not window? could you not window? could they not window?	could I not be windowing? could you not be windowing? could he not be windowing? could we not be windowing? could you not be windowing? could they not be windowing?
Perfect	V-ing perfect
could I not have windowed? could you not have windowed? could he not have windowed? could we not have windowed? could you not have windowed? could they not have windowed?	could I not have been windowing? could you not have been windowing? could he not have been windowing? could we not have been windowing? could you not have been windowing? could they not have been windowing?