noun

index

/ˈɪndeks/ · say it: IN·deks

a statistical measure tracking a market's overall performance

In more detail

1. (noun) a list of topics or names arranged in alphabetical order at the end of a book, with page numbers showing where each topic is discussed

2. (noun) a sign or indication of something

3. (noun) a number that shows the level or value of something compared to a standard or previous level

4. (verb) to arrange something in an index or make it easy to find using an index

Examples

1. I found the chapter on grammar by looking in the book's index.
2. The high unemployment rate is an index of economic problems.
3. The stock market index rose 2% this month.

How to use index

As a noun, index refers to a structured list for locating information or a statistical measure comparing values over time; as a verb, it means to create such a list or to link something to an index. The term is common in academic writing, financial reporting, and data organization, with each sense reflecting different contexts of reference or measurement.

Common phrases

index finger
price index
index entry
look up in the index
alphabetical index
back of the book index

Synonyms

indicator · pointer · sign · catalog · directory

Word family

index (noun, verb) · indexed (adjective) · indexing (noun) · indexer (noun)

A common mistake

Learners sometimes confuse 'index' with 'indices' (plural) and 'indexes' (plural), though both plurals are acceptable; 'indices' is more common in technical and mathematical contexts, while 'indexes' is standard in general English.

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