can sum
Verbo regular: sum - summed- summed

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I can sum
you can sum
he can sum
we can sum
you can sum
they can sum 	I can be summing
you can be summing
he can be summing
we can be summing
you can be summing
they can be summing	I can have summed
you can have summed
he can have summed
we can have summed
you can have summed
they can have summed	I can have been summing
you can have been summing
he can have been summing
we can have been summing
you can have been summing
they can have been summing	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I can't sum
you can't sum
he can't sum
we can't sum
you can't sum
they can't sum 	I can't be summing
you can't be summing
he can't be summing
we can't be summing
you can't be summing
they can't be summing	I can't have summed
you can't have summed
he can't have summed
we can't have summed
you can't have summed
they can't have summed	I can't have been summing
you can't have been summing
he can't have been summing
we can't have been summing
you can't have been summing
they can't have been summing	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
can I sum?
can you sum?
can he sum?
can we sum?
can you sum?
can they sum? 	can I be summing?
can you be summing?
can he be summing?
can we be summing?
can you be summing?
can they be summing? 	can I have summed?
can you have summed?
can he have summed?
can we have summed?
can you have summed?
can they have summed? 	can I have been summing?
can you have been summing?
can he have been summing?
can we have been summing?
can you have been summing?
can they have been summing? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
can't I sum?
can't you sum?
can't he sum?
can't we sum?
can't you sum?
can't they sum? 	can't I be summing?
can't you be summing?
can't he be summing?
can't we be summing?
can't you be summing?
can't they be summing? 	can't I have summed?
can't you have summed?
can't he have summed?
can't we have summed?
can't you have summed?
can't they have summed? 	can't I have been summing?
can't you have been summing?
can't he have been summing?
can't we have been summing?
can't you have been summing?
can't they have been summing?