Complex sentence: In mathematics, particularly in topology, a topological space "X" is sober if every irreducible closed subset of "X" is the closure of exactly one singleton of "X".
Split into simpler sentences: In mathematics, particularly in topology, a sober space is a particular kind of topological space. Specifically, a space "X" is "sober" if every irreducible closed subset of "X" is the closure of exactly one singleton of "X".