Meaning

noun a numerical scale used to compare variables with one another or with some reference number

noun a number or ratio (a value on a scale of measurement) derived from a series of observed facts; can reveal relative changes as a function of time

noun a mathematical notation indicating the number of times a quantity is multiplied by itself

originEtymology tree Latin indexder. English index From Latin index (“a discoverer, informer, spy; of things, an indicator, the forefinger, a title, superscription”), from indicō (“point out, show”); see indicate.

Etymology from Wiktionary, CC BY-SA 3.0