Apartness relation

Let's say you have two sets of toys. One set has a doll, blocks, and a teddy bear. The other set has a truck, a toy car, and a ball. The apartness relation is when you compare the two sets and notice that there are no toys which are the same in both sets. The doll in the first set is different from every toy in the second set. The truck in the second set is different from every toy in the first set too. This means the two sets are apart, they don't have any toys that are the same. It's like having two groups of friends who don't know each other, they are apart from each other.