Stoichiometric coefficient (ν) is the number appearing before the symbol for each compound in the equation for a chemical reaction. By convention, it is negative for reactants and positive for products.
Stoichiometric coefficients describe the stoichiometry of the chemical reaction.
In this equation, a, b, c and d are called as Stoichiometric coefficients of the A, B, C and D respectively.
Generalic, Eni. "Stoichiometric coefficient." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
Glossary
Periodic Table