(physics) The ratio of the speed of light in air or vacuum to that in another medium.

(information science) An indexing algorithm which indexes a document based on the keywords being searched for.

A piece of heavy paper stock used to record information to be stored in an index.

(information science) The act of describing a document by index terms to indicate what the document is about or to summarize its content, the index terms often coming from a controlled vocabulary.

(information science) A term that captures the essence of the topic of a document, used as keyword to retrieve documents in an information system, for instance a catalog or a search engine.

(economics) A measure of the size of firms in relation to the industries they operate in, serving to indicate the amount of competition among them.

An author-level metric that attempts to measure both the productivity and the citation impact of the publications of a scientist or scholar, based on a set of most cited papers and the number of citations in other publications.

A measure of the reward that can be achieved through a given stochastic process with certain properties.

plural of Gittins index

plural of index digit