Question: why xor gate is called odd function?
Answer: In general, an Ex-OR gate will give an output value of logic “1” ONLY when there are an ODD number of 1's on the inputs to the gate, if the two numbers are equal, the output is “0”. Then an Ex-OR function with more than two inputs is called an “odd function” or modulo-2-sum (Mod-2-SUM), not an Ex-OR.