Ranking is ordering data from highest to lowest or *vice versa.* For questions about *constructing* scores to use in ranking, please use the "valuation" tag, too.

Ranking means ordering data from highest to lowest or vice versa. Statistical "ranks" are normally given the values 1, 2, 3, ..., up to the sample size, assigned (respectively) to values or attributes which have the highest (or lowest) rank, the second highest (/lowest) rank, and so on.

A standard notation is to bracket subscripts when denoting ranks: that is, for a batch of numbers $(x_1, x_2, \ldots, x_n)$ (written in any order), the sorted values are written $(x_{[1]}, x_{[2]}, \ldots, x_{[n]})$.

Since the original values being ranked can sometimes be tied (have a weak order), tied ranks can occur where more than one rank is to be assigned to indistinguishable values. This issue is resolved in various ways, but commonly in statistics the average rank allocated to the tied (indistinguishable) observations is assigned to each of them. Allocating average ranks is sometimes called fractional ranking.

Reference: Wikipedia: Ranking in statistics