(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.

(epidemiology) The first documented patient in a disease epidemic within a population or the first case of interest in an epidemiological investigation; the case of patient zero.

plural of index case

(economics) A price or quantity index, a discrete approximation to a continuous Divisia index.

(mathematics) The divisor function of an integer divided by the integer.

a formula for the evaluation and quantification of mortality and morbidity risk as developed for and applied to homeless persons in various social initiatives in the USA

A tabulated and alphabetized notebook, for systematic preservation of items, quotations, etc.

An index of words.

(US, meteorology) A figure used by American meteorologists to describe the apparent heat felt by a person as the result of a combination of temperature and humidity.

(databases) a type of database index that physically sorts the data in a table on the disk to match the criteria specified by the index.