Numbers or quantities that are added together in an addition problem; the singular is addend.
From Latin addendus (to be added), from addere (to add). The '-s' makes it plural in English, creating the standard term used in elementary mathematics.
In the problem 2 + 3 = 5, the addends are 2 and 3—the word itself tells you these are the numbers 'to be added,' preserving Latin grammar in everyday math class.
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