An American is told by his friend that the Asian buffalo is like the bison in such and such respects. When the American visits Asia and comes across a buffalo, he comes to know that the animal seen by him is a buffalo. Which means of knowledge (pramana) is used in this instance?

The animal is identified through upamana, comparison.

A trustworthy description first tells him the buffalo resembles the known bison.

On meeting the actual animal he recognises it by that similarity.

Knowledge of the named object gained via likeness is exactly comparison.

This linking of a word to its object through resemblance is the mark of upamana.