Sets and Elements

• Sets and Elements #Card
  • The concept of set is not defined formally here (see ZFC axioms in Chapter XXVII). We write $x \in X$ to denote that $x$ belongs to $X$.

Back

The concept of set is not defined formally here (see ZFC axioms in Chapter XXVII). We write $x \in X$ to denote that $x$ belongs to $X$.

Lean

Set X := X → Prop と所属 ∈（Set.mem）