1 or 2, in 1 + 2

• Number in a sum
• Number next to a plus sign
• Number on either side of a plus sign
• The 3 or 5 in 3 + 5 = 8
• Quantity to be appended
• Sum part
• This helps to form a sum
• Certain number or quantity
• Portion of a sum

WordNet Word definitions in WordNet
n. a number that is added to another number (the augend)