The Metric for the Poincaré Hyperbolic Disk, a model for Hyperbolic Geometry. The hyperbolic metric is invariant under conformal maps of the disk onto itself.

**References**

Bear, H. S. ``Part Metric and Hyperbolic Metric.'' *Amer. Math. Monthly* **98**, 109-123, 1991.

© 1996-9

1999-05-25