# indices

/ˈɪndəsɪz/ (US) · /ˈɪndɪsˌiːz/ (UK) · CEFR C1 · Noun

Source: https://englishreference.com/word/indices
Updated: 2026-05-06

## Definition

the plural form of 'index'. It refers to lists of information or signs that show how something is changing.

For teachers: the plural of 'index', referring to alphabetical lists of names or subjects with page references, or to statistical measures of change in economy or science.

## Examples

- The researcher checked the indices of several books.
- Economists use various price indices to track how much the cost of living increases over time.
- The library's digital indices allow scholars to cross-reference thousands of manuscripts that were previously catalogued only in separate, physical volumes.

## Pitfalls

- Not "the book's indices" but "the book's indexes" — While 'indices' is technically correct, 'indexes' is the standard plural for back-of-book lists in general English.

## Usage notes

- The plural 'indices' is preferred in technical, mathematical, and financial contexts, whereas 'indexes' is more common for books.

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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.