## Quick Reference

The function *d* used to define a distance between two points in constructing a metric space, with the following properties:

*d*(*x*, *y*)=0 if and only if *x*=*y*,

*d*(*x*, *y*)=*d*(*y*, *x*),

*d*(*x*, *y*)+*d*(*y*, *z*)≥*d*(*x*, *z*) for any points *x*, *y*, *z*.

*Subjects:*
Mathematics — Astronomy and Astrophysics.

## Related content in Oxford Index

##### Reference entries

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.