uncountable set
11Perfect set property — In descriptive set theory, a subset of a Polish space has the perfect set property if it is either countable or has a nonempty perfect subset.As nonempty perfect sets in a Polish space always have the cardinality of the continuum, a set with the… …
12Empty set — ∅ redirects here. For similar looking symbols, see Ø (disambiguation). The empty set is the set containing no elements. In mathematics, and more specifically set theory, the empty set is the unique set having no elements; its size or cardinality… …
13Recursively enumerable set — In computability theory, traditionally called recursion theory, a set S of natural numbers is called recursively enumerable, computably enumerable, semidecidable, provable or Turing recognizable if: There is an algorithm such that the set of… …
14List of set theory topics — Logic portal Set theory portal …
15Constructive set theory — is an approach to mathematical constructivism following the program of axiomatic set theory. That is, it uses the usual first order language of classical set theory, and although of course the logic is constructive, there is no explicit use of… …
16Class (set theory) — In set theory and its applications throughout mathematics, a class is a collection of sets (or sometimes other mathematical objects) which can be unambiguously defined by a property that all its members share. The precise definition of class… …
17Null set — In mathematics, a null set is a set that is negligible in some sense. For different applications, the meaning of negligible varies. In measure theory, any set of measure 0 is called a null set (or simply a measure zero set). More generally,… …
18Recursive set — In computability theory, a set of natural numbers is called recursive, computable or decidable if there is an algorithm which terminates after a finite amount of time and correctly decides whether or not a given number belongs to the set. A more… …
19Negligible set — See also: Generic property In mathematics, a negligible set is a set that is small enough that it can be ignored for some purpose. As common examples, finite sets can be ignored when studying the limit of a sequence, and null sets can be ignored… …
20Index set — In mathematics, the elements of a set A may be indexed or labeled by means of a set J that is on that account called an index set. The indexing consists of a surjective function from J onto A and the indexed collection is typically called an… …
