What's acted on in math

• Part of an equation
• Part of an equation, in math
• Target of a mathematical process
• Quantity on which a math operation is performed
• Either 2 in 2 + 2 = 4, in math
• Divisor, e.g
• Dividend, mathematically

Wikipedia Word definitions in Wikipedia
In mathematics , an operand is the object of a mathematical operation , a quantity on which an operation is performed.

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Operand \Op"er*and\, n. [From neuter of L. operandus, gerundive of operari. See Operate .] (Math.) The symbol, quantity, or thing upon which a mathematical operation is performed; -- called also faciend .

WordNet Word definitions in WordNet
n. a quantity upon which a mathematical operation is performed