The phrase "a red cent" is a colloquialism that refers to a single cent or penny. It is an idiom often used to convey the idea of a small or insignificant amount of money. Synonyms for "a red cent" include "a penny," "a single cent," or "a one-cent piece." Additionally, it can also be referred to as a "centavo," "centime," "copper," or "farthing" depending on the currency and country. The term "a sou" is used in France and some other parts of the world to refer to a small amount of money, equivalent to a single cent or penny. Regardless of the term used, it denotes a small or minimal amount of money.