Ordinal Number

Pronunciation: /ˈɔr dn əl ˈnʌm bər/ ?

An ordinal number is a number which describes position in a well ordered set.[1] Ordinal numbers are first, second, third, and so on. The assignment of ordinal numbers to members of a set can be arbitrary. For example, if you have a stamp collection, you can say that the oldest is the first stamp in your collection, or that the newest is the first stamp in the collection, or any other stamp is the first stamp in the set. Many sets can have more than one ordinality or ways to count the set.

Order of a Set of Postage Stamps
By AgeBy Face ValueBy Color
OrderImageOrderImageOrderImage
18 1/2 cent green stamp from Nova Scotia, 1860.18 1/2 cent green stamp from Nova Scotia, 1860.124 cent red U.S. stamp with biplane.
224 cent red U.S. stamp with biplane.224 cent red U.S. stamp with biplane.232 cent Australian stamp with orchid.
332 cent Australian stamp with orchid.332 cent Australian stamp with orchid.348 cent orange Canadian stamp with falcon.
448 cent orange Canadian stamp with falcon.448 cent orange Canadian stamp with falcon.48 1/2 cent green stamp from Nova Scotia, 1860.
Table 1

The set of ordinal numbers is the same as the set of natural numbers.

References

  1. ordinal number. merriam-webster.com. Encyclopedia Britannica. (Accessed: 2009-12-21). http://www.merriam-webster.com/dictionary/ordinal number.

Cite this article as:


Ordinal Number. 2010-08-06. All Math Words Encyclopedia. Life is a Story Problem LLC. http://www.allmathwords.org/en/o/ordinalnumber.html.

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Revision History


2010-08-05: Corrected error in last sentence. (McAdams, David.)
2009-12-21: Added "References" (McAdams, David.)
2008-10-09: Added example of assigning ordinals to a set (McAdams, David.)
2008-07-01: Initial version (McAdams, David.)

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