Ordinal Number

Pronunciation: /ˈɔr.dn.əl ˈnʌm.bər/ Explain

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 Age		By Face Value		By Color
Order	Image	Order	Image	Order	Image
1		1		1
2		2		2
3		3		3
4		4		4
Table 1

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

References

1. McAdams, David E.. All Math Words Dictionary, ordinal number. 2nd Classroom edition 20150108-4799968. pg 132. Life is a Story Problem LLC. January 8, 2015. Buy the book
2. ordinal number. merriam-webster.com. Encyclopedia Britannica. Merriam-Webster. Last Accessed 9/5/2018. http://www.merriam-webster.com/dictionary/ordinal number. Buy the book

Cite this article as:

McAdams, David E. Ordinal Number. 12/21/2018. All Math Words Encyclopedia. Life is a Story Problem LLC. http://www.allmathwords.org/en/o/ordinalnumber.html.

Image Credits

• All images and manipulatives are by David McAdams unless otherwise stated. All images by David McAdams are Copyright © Life is a Story Problem LLC and are licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

Revision History

12/21/2018: Reviewed and corrected IPA pronunication. (McAdams, David E.)
9/5/2018: Removed broken links, updated license, implemented new markup. (McAdams, David E.)
8/5/2010: Corrected error in last sentence. (McAdams, David E.)
12/21/2009: Added "References". (McAdams, David E.)
10/9/2008: Added example of assigning ordinals to a set. (McAdams, David E.)
7/1/2008: Initial version. (McAdams, David E.)