Also called indiscrete topology, the trivial topology is the smallest topology on a set 
,
namely the one in which the only open sets are the empty set and the entire set 
. These are also the only closed sets.
Trivial Topology
See also
Discrete Topology, TrivialThis entry contributed by Margherita Barile
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Barile, Margherita. "Trivial Topology." From MathWorld--A Wolfram Web Resource, created by Eric W. Weisstein. https://mathworld.wolfram.com/TrivialTopology.html