By themselves already. E.g. there are 10 rock formations in this part of the desert, and 2 rocks in the other side. There is a clustering (set) of 10 vs 2 eve

By themselves already. E.g. there are 10 rock formations in this part of the desert, and 2 rocks in the other side. There is a clustering (set) of 10 vs 2 even if we aren't there to measure them and group them. As are other sets co-existing (like the whole desert has 12 rock formations, while some other has only sand).