Singleton

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2010 Mathematics Subject Classification: Primary: 03E [MSN][ZBL]

A set which contains exactly one element. Notation: $\{ x \}$. One has $y \in \{ x \} \Leftrightarrow y = x$.

References

 [1] P. R. Halmos, Naive Set Theory, Springer (1960) ISBN 0-387-90092-6
How to Cite This Entry:
Singleton. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Singleton&oldid=35373