reagent

American  

[ree-ey-juhnt] / riˈeɪ dʒənt /

noun

Chemistry.

1. a substance that, because of the reactions it causes, is used in analysis and synthesis.

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reagent British  

/ riːˈeɪdʒənt /

noun

1. a substance for use in a chemical reaction, esp for use in chemical synthesis and analysis

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reagent Scientific  

/ rē-ā′jənt /

1. A substance participating in a chemical reaction, especially one used to detect, measure, or produce another substance.

2. Compare agent

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Etymology

Origin of reagent

1790–1800; re(act) + agent; act

Explanation

A reagent is a substance used to create a chemical reaction. Reagents cause transformations. Chemists love reagents because they cause chemical reactions. For example, a certain type of reagent could tell a chemist if something contains a poison. Like a reactant or a catalyst, a reagent makes something happen. It can help you remember reagents are active if you remember that other agents — like secret agents — are also active and make things happen.

Example Sentences

Elevated diesel prices will drive up costs of everything from contract mining, consumables, reagent freight and contract haulage to export logistics, shipping and mine-site aviation, it says.

From The Wall Street Journal • Mar. 30, 2026

But a blood enhancement chemical reagent uncovered a footwear mark and drag mark on the floor.

From BBC • Mar. 7, 2026

Quest Diagnostics, the company that provided the faulty tests, said the false results came after the company temporarily changed the reagent, or chemical, that was usually used in the tests.

From Los Angeles Times • May 31, 2025

It is called Murakami's reagent, which etches away carbon residue and changes the colour of steel in knife making, for example.

From Science Daily • Apr. 16, 2024

“She lives down here. I’m worried that she might be hurt. A lot of the reagent went down the drains from the Fishery.”

From "The Name of the Wind" by Patrick Rothfuss