# classify

/ˈkɫæsəˌfaɪ/ (US) · /klˈæsɪfˌaɪ/ (UK)

Source: https://englishreference.com/word/classify
Updated: 2026-08-08

## Senses

### 1. to categorize

verb · CEFR B2

to put things into groups because they share the same qualities or features.

For teachers: to arrange or assign things to groups or categories according to shared qualities or characteristics.

- Biologists classify animals into different groups based on their physical features.
- The library system is designed to classify books by subject matter, making it easier for researchers to locate specific academic texts.

### 2. to make secret

verb · CEFR C1 · Formal · Technical

to officially decide that a document or information must be kept secret by the government.

For teachers: to designate information or documents as officially secret and accessible only to authorized people.

- The government decided to classify the report to protect national security.
- The intelligence agency chose to classify the documents for fifty years, citing the need to protect active field agents.

Usage: Often used in the passive voice: 'the documents were classified'.

## Examples

- Scientists classify animals into different groups.
- The library staff must classify every new book by its subject before placing it on the shelves.
- While it is easy to classify simple organisms, biologists often struggle with species that exhibit traits belonging to multiple distinct categories, leading to frequent taxonomic revisions.

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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.