A partition of set \(A\)
A set \(P\) (‘part labels’) and, for each \(p \in P\), a nonempty subset (‘pth part’) \(A_p \subseteq A\) such that:
\(A = \bigcup_{p \in P}A_p\)
\(p \ne q \implies A_p \cap A_q = \varnothing\)
Two partitions are considered the same if the partitioned groups are the same, the labels don’t matter.