Topology 1. τ ⊆ 𝓟(X)axiom✹ 2. ∅,X ∈ τaxiom✹ 3. if U,V ∈ τ then U∩V ∈ τaxiom✹ 4. if Uᵢ ∈ τ for all i∈I then ∪Uᵢ ∈ τaxiom✹