Gay-Lussac's Law, also known as the Pressure-Temperature Law, is a relationship between the pressure and temperature of a gas at a constant volume. In scientific circles, it is also referred to as Gay-Lussac's Law of Combining Volumes, Gay-Lussac's Gas Law and Gay-Lussac's Experiment. However, in layman's terms, it can be called the Law of Pressure and Temperature, or the Law of Gas Expansion. Other synonyms include the Law of Gay-Lussac, Gay-Lussac's Principle, and the Gas Law of Gay-Lussac. Despite the different names, they all refer to the same fundamental principle in the properties of gases and their behavior.