English
If s is nonempty and every t ∈ s is small, then ⋂₀ s is small.
Русский
Если s непусто и каждая t ∈ s мала, то ⋂₀ s мала.
LaTeX
$$$[\text{Nonempty } s] \; [\forall t \in s, \operatorname{Small}(t)] \Rightarrow \operatorname{Small}(\bigcap s)$$$
Lean4
instance small_sInter' {s : Set (Set α)} [Nonempty s] [∀ t : s, Small.{u} t] : Small.{u} (⋂₀ s) :=
let ⟨t⟩ : Nonempty s := inferInstance
small_sInter t.prop