1) Arithmetic figure 2) Calculator figure 3) Either 2 in 2 + 2 4) Either 2 in 2 + 2 = 4 5) Figure in a sum 6) It gets summed 7) Math quantity 8) Math-sum unit 9) Number 10) Number next to a + 11) Number next to a plus sign 12) Number on either side of a + 13) Part of a column 14) Part of a sum 15) Part of the total Found on https://www.crosswordclues.com/clue/addend
any of a group of numbers or terms added together to form a sum. · (formerly) a number that is added to another in forming a sum. Cf. augend. Found on https://www.infoplease.com/dictionary/addend