English
A space X is irreducible as a space iff the whole space considered as a subset is irreducible.
Русский
Пространство X неразложимо по отношению к самому себе как множеству, аналогично термину irreducibleSpace.
LaTeX
$$$\\text{IrreducibleSpace}(X) \\iff \\operatorname{IsIrreducible}(\\top : Set X)$$$
Lean4
theorem irreducibleSpace_def (X : Type*) [TopologicalSpace X] : IrreducibleSpace X ↔ IsIrreducible (⊤ : Set X) :=
⟨@IrreducibleSpace.isIrreducible_univ X _, fun h =>
haveI : PreirreducibleSpace X := ⟨h.2⟩
⟨⟨h.1.some⟩⟩⟩