Metric spaces
A metric supplies a distance satisfying three axioms.
Key knowledge
A metric d on X is nonnegative, vanishes exactly when its arguments coincide, is symmetric and satisfies the triangle inequality. Open balls contain points at distance less than a positive radius.
Values and equations
d(x,z) ≤ d(x,y)+d(y,z); B_r(x)={y:d(x,y)<r}
- d
- Metric
- x,y,z
- Points of X
- r
- Positive radius
Conditions and scope
- A metric is finite-valued here.
- No vector-space structure or Euclidean geometry is assumed.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Definitions 13.1, 13.10 and 13.75: metric, open balls and finite-subcover compactness.
2026-10-10 · Definitions 13.1 and 13.10 only.
Entry details
Permanent link to this entry ↗- Record identity
- math-metric-spaces
- Revision
- university-reference.1
- Structured reference record
- University reference