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  2. Finite set - Wikipedia

    en.wikipedia.org/wiki/Finite_set

    In mathematics, particularly set theory, a finite set is a set that has a finite number of elements. Informally, a finite set is a set which one could in principle ...

  3. Set (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Set_(mathematics)

    In mathematics, a set is a collection of different [1] things; [2] [3] [4] these things are called elements or members of the set and are typically mathematical objects of any kind: numbers, symbols, points in space, lines, other geometrical shapes, variables, or even other sets. [5] A set may have a finite number of elements or be an infinite set.

  4. Discrete mathematics - Wikipedia

    en.wikipedia.org/wiki/Discrete_mathematics

    Set theory is the branch of mathematics that studies sets, which are collections of objects, such as {blue, white, red} or the (infinite) set of all prime numbers. Partially ordered sets and sets with other relations have applications in several areas. In discrete mathematics, countable sets (including finite sets) are the main focus

  5. Family of sets - Wikipedia

    en.wikipedia.org/wiki/Family_of_sets

    An abstract simplicial complex is a set family (consisting of finite sets) that is downward closed; that is, every subset of a set in is also in . A matroid is an abstract simplicial complex with an additional property called the augmentation property .

  6. Union (set theory) - Wikipedia

    en.wikipedia.org/wiki/Union_(set_theory)

    A finite union is the union of a finite number of sets; the phrase does not imply that the union set is a finite set. [9] ... Disjoint union – In mathematics, ...

  7. Countable set - Wikipedia

    en.wikipedia.org/wiki/Countable_set

    In mathematics, a set is countable if either it is finite or it can be made in one to one correspondence with the set of natural numbers. [a] Equivalently, a set is countable if there exists an injective function from it into the natural numbers; this means that each element in the set may be associated to a unique natural number, or that the elements of the set can be counted one at a time ...

  8. Category of sets - Wikipedia

    en.wikipedia.org/wiki/Category_of_sets

    Every set is a projective object in Set (assuming the axiom of choice). The finitely presentable objects in Set are the finite sets. Since every set is a direct limit of its finite subsets, the category Set is a locally finitely presentable category. If C is an arbitrary category, the contravariant functors from C to Set are often an important ...

  9. Universe (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Universe_(mathematics)

    But each of the elements of S{} will be a finite set. Each of the natural numbers belongs to it, but the set N of all natural numbers does not (although it is a subset of S{}). In fact, the superstructure over {} consists of all of the hereditarily finite sets. As such, it can be considered the universe of finitist mathematics.