User:Peter Schmitt/Notes: Difference between revisions

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{{r|zero (mathematics)}}  [[0]] [[0 (number)]]  [[zero]]  [[zero (disambiguation)]]
{{r|zero (mathematics)}}  [[0]] [[0 (number)]]  [[zero]]  [[zero (disambiguation)]]


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{{r|Neighbourhood (topology)}}
:: {{r|Boundary point||}}
:: {{r|clopen||}}
:: {{r|clopen set||}}
:: {{r|open set||}}
:: {{r|closed set||}}
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Revision as of 11:15, 2 October 2009


  • Cardinality [r]: The size, i.e., the number of elements, of a (possibly infinite) set. [e]
  • Countable set [r]: A set with as many elements as there are natural numbers, or less. [e]
Countable [r]: In mathematics, a property of sets — see: Countable set (A set with as many elements as there are natural numbers, or less.) [e]
Uncountable [r]: In mathematics, a property of sets — see: Countable set (A set with as many elements as there are natural numbers, or less.) [e]
Uncountable set [r]: A set with more elements than there are natural numbers. (See: Countable set.) [e]
  • Transfinite number [r]: An infinite number, either a cardinal number or an ordinal number. [e]
  • Cardinal number [r]: The generalization of natural numbers (as means to count the elements of a set) to infinite sets. [e]
Aleph-0 [r]: Cardinality (size) of the set of all natural numbers. [e]
Aleph-1 [r]: Add brief definition or description
  • Infinite [r]: Greater in size (number of elements, length, area, etc.) than any natural number [e]
  • Infinite set [r]: The number of its elements is larger than any natural number. (See: Finite set.) [e]
  • Finite set [r]: The number of its elements is a natural number (0,1,2,3,...) [e]
Finite [r]: Bounded (or limited) in size (length, area, etc., or number of elements) by a natural number [e]

  • Neighbourhood (topology) [r]: In a topological space, a set containing a given point in its interior, expressing the idea of points "near" this point. [e]
Boundary point [r]: (of a set) In geometry and topology, a point such that every neighbourhood contains both points in the set and points not in the set. [e]
Clopen [r]: In topology, a combination of closed and open (clopen set). [e]
Clopen set [r]: In topology, a set with empty boundary which therefore is both closed and open. [e]
Open set [r]: In geometry and topology, a set that does not contain any of its boundary points. [e]
Closed set [r]: In geometry and topology, a set that contains its boundary; the complement of an open set. [e]