Ranking is the process of positioning items such as individuals, groups or businesses on an ordinal scale in relation to others. A list arranged in this way is said to be in rank order .

A ranking can be obtained by evaluating each item in the collection in such a way that any two items can then be compared to see which should come higher in the ranking. In mathematical terms, this is known as a weak order or total preorder of objects. It is not necessarily a total order of objects because two different objects can have the same ranking. The rankings themselves are totally ordered. For example, materials are totally preordered by hardness , while degrees of hardness are totally ordered.

1. By reducing detailed measures to a sequence of ordinal numbers , rankings make it possible to evaluate complex information according to certain critera. Thus, for example, an Internet search engine may rank the pages it finds according to an evaluation of their relevance, making it possible for the user quickly to select the pages they are likely to want to see.

   Ranking is a technique commonly used in non-parametric statistics .