# reagent

/ˈɹidʒənt/ (US) · /ɹɪˈeɪdʒənt/ (UK) · CEFR C1 · Noun

Source: https://englishreference.com/word/reagent
Updated: 2026-05-19

## Definition

a substance used in a chemical test or experiment to cause a reaction. It helps you see if another substance is present or how it behaves.

For teachers: a substance that is added to another substance to cause a chemical reaction. Often used in qualitative analysis to identify the presence of specific ions or compounds.

## Examples

- The student added a few drops of the reagent to the solution.
- In the lab, the technician used a specific reagent to detect the presence of chloride ions in the water sample.
- The chemist carefully selected a reagent that would react selectively with the target molecule without interfering with the surrounding organic structure.

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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.