Reagent

A reagent ( /riˈeɪdʒənt/) is a "substance or compound that is added to a system in order to bring about a deletal reaction, or added to see if a reaction occurs." Although the terms reactant and reagent are often used interchangeably, a reactant is less specifically a "substance that is consumed in the course of a chemical reaction". Solvents, although they are involved in the reaction, are usually not referred to as reactants. Similarly, catalysts are not consumed by the reaction, so are not described as reactants.