Unordered pair
From Encyclopedia of Mathematics
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2020 Mathematics Subject Classification: Primary: 05E [MSN][ZBL]
doubleton
A set containing two elements, denoted $\{x,y\}$. One has $z \in \{x,y\} \Leftrightarrow z = x \vee z = y$, and so $\{x,y\} = \{y,x\}$. Compare with an ordered pair.
References
| [1] | P. R. Halmos, Naive Set Theory, Springer (1960) ISBN 0-387-90092-6 |
How to Cite This Entry:
Unordered pair. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Unordered_pair&oldid=35379
Unordered pair. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Unordered_pair&oldid=35379