δ-hyperbolic space

In mathematics, a δ-hyperbolic space is a geodesic metric space in which every geodesic triangle is δ-thin.

There are many equivalent definitions of "δ-thin". A simple definition is as follows: pick three points and draw geodesic lines between them to make a geodesic triangle. Then any point on any of the edges of the triangle is within a distance of δ from one of the other two sides.