def plusOne(x: Int) { val y = x + 1; return y } In the line of code above, `y` is an immutable variable. It does not mutate, yet it "varies" as different value

def plusOne(x: Int) { val y = x + 1; return y } In the line of code above, `y` is an immutable variable. It does not mutate, yet it "varies" as different values of x come in.