A usually available or readily made compound or known mixture of compounds used to treat materials, samples, other compounds or reactants in a laboratory or sometimes an industrial setting
A reagent is a substance that is used to cause a chemical reaction. Reagents are often used in order to indicate the presence of another substance. a substance that shows that another substance in a compound exists, by causing a chemical reaction (present participle of reagere , from agere )
{i} substance used to detect or measure another substance or to convert one substance into another by chemical reaction (Chemistry)
a chemical substance used to cause a reaction for the purpose of chemical analysis