If "multiples" is to "product", "_____" is to "sum" I know this might be a really simple question for those fluent in English, but I can't find the term that describes numbers that make up a sum. 
The numbers of a certain product are called "multiples" of that "product". 
Then what are the numbers of a certain sum called?

According to Wikipedia, "summands", "addends", or "terms" are all acceptable.
Also, I've never heard "multiples" used as the corresponding word for multiplication. Wikipedia lists the words "factors" and "multiplicands" both of which I'm familiar with.
