Set

:This article is about sets in mathematics. For other senses, see set (disambiguation).

Cardinality of a set

Each of the sets described above has a definite number of members; for example, the set A has four members, while the set B has three members.

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A set can also have zero members. Such a set is called the empty set (or the null set) and is denoted by the symbol ø. For example, the set A of all living dragons has zero members, and thus A = ø. Like the number zero, though seemingly trivial, the empty set turns out to be quite important in mathematics.

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For more information on the empty set see Empty set.

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A set can also have an infinite number of members; for example, the set of natural numbers is infinite.

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For more information on infinity and the size of sets, see cardinality and cardinal number.

Related Topics:
Infinity - Cardinality - Cardinal number

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For more information on finite sets and counting them, see combinatorics and permutations and combinations.

Related Topics:
Combinatorics - Permutations and combinations

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