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; cf. 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

“We believe that the different reagent led to a higher presumptive positivity rate on screening results than the standard reagent used by Quest Diagnostics,” the statement read.

From Los Angeles Times • Apr. 29, 2025

This selectivity switch can be accomplished by choosing one reagent over another, a process that is as streamlined as it is cost-effective.

From Science Daily • Dec. 7, 2023

“Jaxim saw you leaping through the fire just moments after the reagent spilled. The drench is quick, but not so quick as that.”

From "The Name of the Wind" by Patrick Rothfuss