subset & superset 

In mathematics, especially in set theory, a set A is a subset of a set B, or equivalently B is a superset of A, if A is “contained” inside B, that is, all elements of A are also elements of BA and B may coincide. The relationship of one set being a subset of another is called inclusion or sometimes containment.

 

If A and B are sets and every element of A is also an element of B, then:

  • A is a subset of (or is included in) B, denoted by {\displaystyle A\subseteq B}A\subseteq B,
or equivalently

  • B is a superset of (or includes) A, denoted by {\displaystyle B\supseteq A.}B\supseteq A.
  •  

    符号”⊆”表示任何子集;符号”⊊”表示真子集。”⊂”也是一个很常见的符号,但有人仅用它表示真子集

 


 

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