can sum
Regular verb: sum - summed- summed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I can sum
you can sum
she can sum
we can sum
you can sum
they can sum 	I can be summing
you can be summing
she can be summing
we can be summing
you can be summing
they can be summing	I can have summed
you can have summed
she 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
she can have been summing
we can have been summing
you can have been summing
they can have been summing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I can't sum
you can't sum
she 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
she 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
she 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
she can't have been summing
we can't have been summing
you can't have been summing
they can't have been summing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can I sum?
can you sum?
can she sum?
can we sum?
can you sum?
can they sum? 	can I be summing?
can you be summing?
can she be summing?
can we be summing?
can you be summing?
can they be summing? 	can I have summed?
can you have summed?
can she 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 she have been summing?
can we have been summing?
can you have been summing?
can they have been summing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can't I sum?
can't you sum?
can't she 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 she 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 she 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 she have been summing?
can't we have been summing?
can't you have been summing?
can't they have been summing?