reagent

Meanings

1. 1
   noun

   a substance or mixture used to cause, detect, measure, or investigate a chemical reaction

   The technician added a clear reagent that turned blue in the presence of starch.

From New Latin reagens, the present participle of reagere ("to react"), formed from Latin re- ("back, again") + agere ("to do, drive"). The ending was understood by analogy with agent: a reagent is an agent introduced to produce or reveal a reaction.

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