Definition With B as a Vector Space With d:V×V→R as a function The function d is a metric if: d(v,w)≥0,∀v,w∈V (Non-negativity) d(v,w)=d(w,v) (Commutative/Symmetric) d(v,w)=0⟺v=w (Zero distance for equality) d(u,w)≤d(u,v)+d(v,w) (Triangle Inequality) Implementations Euclidean Metric for Reals in R2 Theorems 1-Metric