The term "normal electrode system" refers to a type of reference electrode that is commonly used in electrochemistry. This particular type of electrode system is designed to provide a stable and reproducible standard against which other electrochemical measurements can be made. Synonyms for the term "normal electrode system" include reference electrode, standard electrode, and calomel electrode. These other terms all refer to the same basic concept of a stable and reproducible electrode that is used to establish a baseline for electrochemical measurements. The use of these synonyms can help to clarify the specific type of electrode system being discussed, and can aid in understanding the principles and applications of electrochemistry.