Reactant

A reactant or reagent is any substance initially present in a chemical reaction. These reactants react with each other to form the products of a chemical reaction. In a chemical equation, the reactants are the elements or compounds on the left hand side of the reaction equation.The reactant normally combines with the other chemicals to form a mixture, solution or compound. After reacting, the reactant is changed either chemically or physically from its unreacted state.

• Reactant(s) → Product(s)

A substance participating in a chemical reaction, especially a directly reacting substance present at the initiation of the reaction.