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集合族

集合论和有关的数学分支中,给定集合S子集F 叫做S子集族(或称S 上的集合族)。更一般的说,无论什么任何集合的类都叫做集合族。

例子

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  • 幂集P(S )是在S 上的集合族。
  • n元素集合Sk 元素子集S (k )形成了集合族。
  • 所有序数的类Ord是“大”集合族;它自身不是集合而是真类
  • S = {a,b,c,1,2}。(在多重集含义上的) S 上集合族的一个例子是当 A1 = {a,b,c},A2 = {1,2},A3 = {1,2},A4 = {a,b,1} 时的 F = {A1, A2, A3, A4}。
  • 样本空间的某些子集组成的集合叫做集合族。

特例

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性质

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  • S 的任何子集族自身都是幂集P(S )的子集。
  • 不论什么集合族都是所有集合的真类(全集V子类
  • 菲利浦·赫尔提出的赫尔婚姻定理给出了非空集(允许重复)的有限族具有互异代表元系的充要条件。[1]

C族

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最简单的集合族是由有限集M 的全体子集所构成的,简称为C 族。[2]C 族有以下基本的性质: 设,则集合M 的全部子集构成的类M*, 即

参见

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  1. ^ 存档副本. [2020-07-12]. (原始内容存档于2020-07-13). 
  2. ^ 刘诗雄《数学奥林匹克小丛书·高中卷·集合》,2012,第43页
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集合族
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