index
An alphabetical listing of items and their location.
Example
“The index of a book lists words or expressions and the pages of the book upon which they are to be found.”
Other meanings
The index finger; the forefinger.
A movable finger on a gauge, scale, etc.
Word history
From Latin "index".
Where this comes from
This definition is adapted from “index” on Wiktionary, by its contributors, published under CC BY-SA 4.0. This page is published under the same licence.