summand
noun
sum·mand ˈsə-ˌmand 
ˌsə-ˈmand
: a term in a summation : addend
Example Sentences
Recent Examples on the Web But in the 3-adics, 972 is the same size as 486, because both the sum (972) and the summand (486) have the same number of 3s in their prime factorization. 
Quanta Magazine, 19 Oct. 2020
Quanta Magazine, 19 Oct. 2020 Word History
Etymology
Medieval Latin summandus, gerund of summare to sum, from summa
First Known Use
1846, in the meaning defined above