A nonempty set is a set containing one or more elements. Any set other than the empty set 
is therefore a nonempty set.
Nonempty sets are sometimes also called nonvoid sets (Grätzer 1971, p. 6).
A nonempty set containing a single element is called a singleton
set.
Nonempty Set
See also
Empty Set, Set, Singleton SetExplore with Wolfram|Alpha
References
Grätzer, G. Lattice Theory: First Concepts and Distributive Lattices. San Francisco, CA: W. H. Freeman, 1971.Referenced on Wolfram|Alpha
Nonempty SetCite this as:
Weisstein, Eric W. "Nonempty Set." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/NonemptySet.html