The substances undergoing reactions are called reactants, and their formulas placed on the left side of the equation.

The substances generated by the reaction are called products. Their formulas placed on the right side of the equation.

Plus signs (+) separate individual reactant and product formulas, and an arrow (⟶) separate the reactant and product (left and right) sides of the equation.

The relative numbers of reactant and product species represented by coefficients (numbers placed immediately to the left of each formula). A coefficient of 1 typically omitted.