could frown
Regular verb: frown - frowned- frowned

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could frown
you could frown
he could frown
we could frown
you could frown
they could frown 	I could be frowning
you could be frowning
he could be frowning
we could be frowning
you could be frowning
they could be frowning	I could have frowned
you could have frowned
he could have frowned
we could have frowned
you could have frowned
they could have frowned	I could have been frowning
you could have been frowning
he could have been frowning
we could have been frowning
you could have been frowning
they could have been frowning	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not frown
you could not frown
he could not frown
we could not frown
you could not frown
they could not frown 	I could not be frowning
you could not be frowning
he could not be frowning
we could not be frowning
you could not be frowning
they could not be frowning	I could not have frowned
you could not have frowned
he could not have frowned
we could not have frowned
you could not have frowned
they could not have frowned	I could not have been frowning
you could not have been frowning
he could not have been frowning
we could not have been frowning
you could not have been frowning
they could not have been frowning	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I frown?
could you frown?
could he frown?
could we frown?
could you frown?
could they frown? 	could I be frowning?
could you be frowning?
could he be frowning?
could we be frowning?
could you be frowning?
could they be frowning? 	could I have frowned?
could you have frowned?
could he have frowned?
could we have frowned?
could you have frowned?
could they have frowned? 	could I have been frowning?
could you have been frowning?
could he have been frowning?
could we have been frowning?
could you have been frowning?
could they have been frowning? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not frown?
could you not frown?
could he not frown?
could we not frown?
could you not frown?
could they not frown? 	could I not be frowning?
could you not be frowning?
could he not be frowning?
could we not be frowning?
could you not be frowning?
could they not be frowning? 	could I not have frowned?
could you not have frowned?
could he not have frowned?
could we not have frowned?
could you not have frowned?
could they not have frowned? 	could I not have been frowning?
could you not have been frowning?
could he not have been frowning?
could we not have been frowning?
could you not have been frowning?
could they not have been frowning?