This type of quantity  is the length of the shortest path connecting two vertices in graph theory.
For Banach spaces X and Y, one quantity of this type is the log of the infinium of the norm of T and the inverse of T,  where T represents all isomorphisms mapping X to Y, and is named after Banach and Mazur. For ultrametrics, this  quantity is always of a Robinsonian type. One variant of this measure is a scale-invariant quantity calculated using a  correlation matrix and is used to compare two distributions, and is named for P.C. Mahalanobis. For a metric space, this  type of measure is required to be non-negative, symmetric, and must satisfy the (*) triangle inequality. This type of quantity  is the length of the shortest path connecting two vertices in graph theory. For 2D Euclidean spaces, it is the square root of the sum  of the squares of the differences of the x and y coordinates. For 10 points, identify this type of measure that, in Euclidean space, is  defined as the length of a line connecting two points.
For Banach spaces X and Y, one quantity of this type is the log of the infinium of the norm of T and the inverse of T,  where T represents all isomorphisms mapping X to Y, and is named after Banach and Mazur.
distance [accept no other answer]  1