Definition:Set Partition/Also defined as
Jump to navigation Jump to search
Some sources do not impose the condition that all sets in $\Bbb S$ are non-empty.
This is most probably more likely to be an accidental omission rather than a deliberate attempt to allow $\O$ to be an element of a partition.
The point is minor; proofs of partitionhood usually include a demonstration that all elements of such a partition are indeed non-empty.