# index /ˈɪndɛks/ (US) · /ˈɪndɛks/ (UK) Source: https://englishreference.com/word/index Updated: 2026-07-22 ## Senses ### 1. book listing noun · CEFR B2 an alphabetical list at the end of a book that shows the page numbers for specific topics. For teachers: an alphabetical list of names, subjects, or terms with references to the places where they occur, typically found at the end of a printed work. - If you want to find the section on climate change, look it up in the index. - The researcher spent hours cross-referencing the index to ensure every mention of the primary source was accurately cited in the bibliography. ### 2. statistical measure noun · CEFR C1 · Academic · Technical a system or number used to measure and compare changes in things like prices or wages. For teachers: a statistical measure of change in an economy or a securities market, often expressed as a percentage of a base value. - The consumer price index shows how much the cost of living has gone up this year. - Economists monitor the stock market index as a proxy for investor confidence and broader macroeconomic stability. ### 3. sign or indicator noun · CEFR C1 · Formal · Literary a sign or measure of something else. For teachers: a sign, token, or indication of a particular situation, quality, or state of affairs. - The number of new houses being built is a good index of the country's wealth. - The rapid decline in local bird populations served as a grim index of the overall health of the ecosystem. ### 4. computing/data noun · CEFR C1 · Technical a key or number used to find a specific piece of information in a computer's memory. For teachers: a data structure or integer used to locate and access specific elements within an array, database, or file system efficiently. - The program failed because it tried to access an index that didn't exist in the list. - By creating a secondary index on the customer ID column, the database administrator significantly reduced query latency for the web application. ### 5. math power noun · CEFR C1 · Technical a small raised number that shows how many times to multiply a number by itself. For teachers: a number or symbol, often written as a superscript, indicating the power to which a quantity is to be raised. - In the expression 10 to the power of 3, the number 3 is the index. - Students must learn the laws of indices before they can solve complex algebraic equations involving roots and powers. ### 6. to create a list verb · CEFR B2 to make an alphabetical list of the topics in a book or document. For teachers: to record names or topics in an index; to provide a book or document with an index. - The library is working to index all of its old newspapers so people can search them online. - The software automatically indexes every word in the document, allowing for instantaneous full-text searching across the entire archive. Usage: The verb is transitive and requires a direct object. ### 7. to link to an index verb · CEFR C1 · Technical · Formal to link wages or prices to a system so they change automatically when costs go up. For teachers: to adjust a value, such as a salary or interest rate, automatically according to changes in a price index. - The government decided to index pensions to inflation to help retired people. - The union negotiated a contract where annual pay increases are indexed to the national cost-of-living adjustments. ## Examples - I looked in the index to find the chapter on history. - The consumer price index serves as a primary indicator for measuring inflation and adjusting social security benefits. - While the back-of-the-book index remains essential for academic research, digital search functions have largely replaced it for casual readers seeking specific keywords within a text. --- From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.