 The notions of the sum and product of relation numbers is defined as the relation number of the sum and product of the relations, with adjustments made so that the types of the relations are uniform, and the numbers contain disjoint relations, as was seen in the definition of sum for cardinal numbers in ∗110 above. If x and y are relation numbers, their sum is \(x \dot{+} y\) and the product is \(x \dot{\times} y\).