[count] 1 plural usually indexes : an ordered list: such as a : an alphabetical list at the end of a book that shows the page where each thing in the list can be found ▪ Look up the recipe for potato soup in the index. ▪ Potato soup is listed under “soup” in the index. b : a group of related things that are in alphabetical or numerical order ▪ The card catalog is an index to the materials in the library.
2 : a sign or number that shows how something is changing or performing ▪ The price of goods is an index [=indication] of business conditions. : a number that indicates changes in the level of something (such as a stock market) when it rises or falls ▪ a stock index ▪ certain economic indexes/indices ▪ (Brit) an index-linked pension [=a pension that is linked to an index (such as the retail price index) so that it rises or falls as the index does] —see also consumer price index, retail price index
3 : a device used to point to something (such as a number) ▪ the index on a scale