could sum
Verbo regular: sum - summed- summed

Afirmação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I could sum
you could sum
he could sum
we could sum
you could sum
they could sum 	I could be summing
you could be summing
he could be summing
we could be summing
you could be summing
they could be summing	I could have summed
you could have summed
he could have summed
we could have summed
you could have summed
they could have summed	I could have been summing
you could have been summing
he could have been summing
we could have been summing
you could have been summing
they could have been summing	

Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I couldn't sum
you couldn't sum
he couldn't sum
we couldn't sum
you couldn't sum
they couldn't sum 	I couldn't be summing
you couldn't be summing
he couldn't be summing
we couldn't be summing
you couldn't be summing
they couldn't be summing	I couldn't have summed
you couldn't have summed
he couldn't have summed
we couldn't have summed
you couldn't have summed
they couldn't have summed	I couldn't have been summing
you couldn't have been summing
he couldn't have been summing
we couldn't have been summing
you couldn't have been summing
they couldn't have been summing	

Forma interrogativa 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
could I sum?
could you sum?
could he sum?
could we sum?
could you sum?
could they sum? 	could I be summing?
could you be summing?
could he be summing?
could we be summing?
could you be summing?
could they be summing? 	could I have summed?
could you have summed?
could he have summed?
could we have summed?
could you have summed?
could they have summed? 	could I have been summing?
could you have been summing?
could he have been summing?
could we have been summing?
could you have been summing?
could they have been summing? 	

Forma interro-Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
couldn't I sum?
couldn't you sum?
couldn't he sum?
couldn't we sum?
couldn't you sum?
couldn't they sum? 	couldn't I be summing?
couldn't you be summing?
couldn't he be summing?
couldn't we be summing?
couldn't you be summing?
couldn't they be summing? 	couldn't I have summed?
couldn't you have summed?
couldn't he have summed?
couldn't we have summed?
couldn't you have summed?
couldn't they have summed? 	couldn't I have been summing?
couldn't you have been summing?
couldn't he have been summing?
couldn't we have been summing?
couldn't you have been summing?
couldn't they have been summing?