Definition - What does reagent mean?
A reagent is a substance used to trigger a chemical reaction. Reagents are used to measure and evaluate the reactions of a substance or to synthesize a different substance. In laboratory testing, a reagent may be used to detect the presence of a substance in a sample solution. For instance, a reagent added to a urine sample might trigger a color change indicating the presence of a targeted drug or hormone.
SureHire explains reagent
In chemistry, reagents are used for creation of chemical reactions and for analyzing the response of a substance to the reagent. For example, if chemical A is known to cause a specific color change when combined with chemical B, then chemical A may be used as a reagent to detect the presence of chemical B in a solution. If chemical A and B are known to create compound C when combined, then chemical A may be used as a reagent to create compound C. A reagent may act as a catalyst, causing a reaction but not being consumed by it. A reagent may also serve as a reactant in which it is consumed by the chemical reaction it triggers.