[koun-tuh-buh l] /ˈkaʊn tə bəl/

able to be counted.

capable of being counted
(maths, logic) able to be counted using the natural numbers; finite or denumerable
(linguistics) denoting a count noun

A term describing a set which is isomorphic to a subet of the natural numbers. A countable set has “countably many” elements. If the isomorphism is stated explicitly then the set is called “a counted set” or “an enumeration”.
Examples of countable sets are any finite set, the natural numbers, integers, and rational numbers. The real numbers and complex numbers are not [proof?].


Read Also:

  • Countably-additive-function

    noun, Mathematics. 1. a set function that upon operating on the union of a countable number of disjoint sets gives the same result as the sum of the functional values of each set.

  • Countably-compact-set

    noun, Mathematics. 1. a set for which every cover consisting of a countable number of sets has a subcover consisting of a finite number of sets.

  • Countably many


  • Count against

    verb 1. (intransitive, preposition) to have influence to the disadvantage of: your bad timekeeping will count against you Be disadvantageous to, as in His earnings this year will count against his Social Security benefits. This idiom uses count in the sense of “make a reckoning,” in this case negative. [ Early 1900s ]

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