Subset::''a''    ''B''::proper    ''S''::''x''    Number::equal    Which::order    Element::''y''

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Euler diagram showing
A is a proper subset of B and conversely B is a proper superset of A

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 B. A and B may coincide. The relationship of one set being a subset of another is called inclusion or sometimes containment.

The subset relation defines a partial order on sets.

The algebra of subsets forms a Boolean algebra in which the subset relation is called inclusion.

Subset sections
Intro  Definitions  \u2282 and \u2283 symbols   Examples    Other properties of inclusion   See also  References   External links   

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