Metric Space

A metric space (\(\mathcal{M}, d\)) that satisfies:

1. \(d: \mathcal{M}\times\mathcal{M}\to\mathbb{R}\)
2. \(d(x,x) = 0\)
3. If \(x\neq y\) then \(d(x,y)>0\)
4. \(d(x,y)=d(y,x)\)
5. \(d(x,z)\leq d(x,y)+d(y,z)\)