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The first ordinal number that is not a natural number is expressed as ω; this is also the ordinal number of the set of natural numbers itself. The least ordinal of cardinality ℵ 0 (that is, the initial ordinal of ℵ 0) is ω but many well-ordered sets with cardinal number ℵ 0 have an ordinal number greater than ω.
The natural number following 0 is 1 and no natural number precedes 0. The number 0 may or may not be considered a natural number, [70] [71] but it is an integer, and hence a rational number and a real number. [72] All rational numbers are algebraic numbers, including 0.
Algebraic number: Any number that is the root of a non-zero polynomial with rational coefficients. Transcendental number: Any real or complex number that is not algebraic. Examples include e and π. Trigonometric number: Any number that is the sine or cosine of a rational multiple of π.
For every natural number n, S(n) is a natural number. That is, the natural numbers are closed under S. For all natural numbers m and n, if S(m) = S(n), then m = n. That is, S is an injection. For every natural number n, S(n) = 0 is false. That is, there is no natural number whose successor is 0.
The number of elements of the empty set (i.e., its cardinality) is zero. The empty set is the only set with either of these properties. For any set A: The empty set is a subset of A; The union of A with the empty set is A; The intersection of A with the empty set is the empty set; The Cartesian product of A and the empty set is the empty set
aleph-nought, aleph-zero, or aleph-null) is the cardinality of the set of all natural numbers, and is an infinite cardinal.The set of all finite ordinals, called or (where is the lowercase Greek letter omega), also has cardinality .
The symbol S can be interpreted as "the successor of", or "the number after".Since this is, however, a number theory, such interpretations are useful, but not strict. It cannot be said that because four is the successor of three that four is SSSS0, but rather that since three is the successor of two, which is the successor of one, which is the successor of zero, which has been described as 0 ...
The counting numbers refer to the natural numbers in common language, particularly in primary school education, and are similarly ambiguous although typically exclude zero. [4] The natural numbers can be used for counting (as in "there are six coins on the table"), in which case they serve as cardinal numbers .