Просмотр кода страницы Partition of a set

'''Partition of a set''' --- разбиение множества. 

A ''' partition''' of a nonempty set <math>S</math> is a collection of pairwise
disjoint nonempty subsets, whose union is <math>S</math>. If two partitions
<math>\{A_{i}\}</math> and <math>\{B_{j}\}</math> of the same set are such that each <math>A_{i}</math>
is a subset of some <math>B_{j}</math>, then we say that the partition
<math>\{A_{i}\}</math> is finer than the partition <math>B_{j}</math>, and that <math>\{B_{j}\}</math>
is coarser than <math>\{A_{i}\}</math>.