The function from a given nonempty set 
to the power set 
that maps every element 
of 
to the set 
.
Singleton Function
See also
Nonempty Set, Power SetThis entry contributed by Margherita Barile
Explore with Wolfram|Alpha
Cite this as:
Barile, Margherita. "Singleton Function." From MathWorld--A Wolfram Web Resource, created by Eric W. Weisstein. https://mathworld.wolfram.com/SingletonFunction.html