# Definitions for **ordinal number**

### This page provides all possible meanings and translations of the word **ordinal number**

### Random House Webster's College Dictionary

or′dinal num′ber(n.)

any of the numbers that express degree, quality, or position in a series, as first, second, and third.

**Category:**Math

#### Origin of **ordinal number**:

1600–10

### Princeton's WordNet

ordinal number, ordinal, no.(noun)

the number designating place in an ordered sequence

### Wiktionary

ordinal number(Noun)

A word that expresses the relative position of an item in an ordered sequence.

ordinal number(Noun)

A number used to denote position in a sequence.

ordinal number(Noun)

A generalized kind of number to denote the size of a well-ordered set.

### Freebase

Ordinal number

In set theory, an ordinal number, or just ordinal, is the order type of a well-ordered set. They are usually identified with hereditarily transitive sets. Ordinals are an extension of the natural numbers different from integers and from cardinals. Like other kinds of numbers, ordinals can be added, multiplied, and exponentiated. Ordinals were introduced by Georg Cantor in 1883 to accommodate infinite sequences and to classify sets with certain kinds of order structures on them. He derived them by accident while working on a problem concerning trigonometric series—see Georg Cantor. Two sets S and S' have the same cardinality if there is a bijection between them If a partial order < is defined on set S, and a partial order

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"ordinal number." *Definitions.net.* STANDS4 LLC, 2014. Web. 21 Dec. 2014. <http://www.definitions.net/definition/ordinal number>.