could window
Regular verb: window - windowed- windowed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
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	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 	Perfect 	V-ing perfect 	
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	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 	Perfect 	V-ing perfect 	
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? 	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 	Perfect 	V-ing perfect 	
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? 	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?