EDB — 24Z

[24Z] A set \(A\) is said to be transitive if these equivalent conditions hold:

• \[ ∀ x, x ∈ A ⇒ x⊆ A\quad , \]

  i.e. every element of \(A\) is also a subset of \(A\);

• \[ ∀ x,y, x ∈y ∧ y∈ A ⇒ x∈ A\quad . \]