TITLE: What is the name of the number that is being added to another number?
QUESTION [12 upvotes]: What is the name of the number that is being added to another number? 
I am writting a paper, and I want to know how to call the number that you add to another number (for example: 2+4, how can I call the four without saying the word "4"). Thanks.

REPLY [4 votes]: Addend is not a very familiar term, whereas summand makes no distinction between the number being added to and the number being added. Perhaps the term you are looking for is simply increment.  This is certainly in common use in calculus when you speak of $\Delta x$ as being the $x$-increment and evaluate $f$ at $x+\Delta x$.