Charles's Law is a scientific principle that states that the volume of a gas increases when its temperature also increases, keeping the pressure constant. It is also known as the law of volumes, Gay-Lussac's law, or the pressure-temperature law. The law was postulated by Jacques Charles in 1787 and eventually formulated mathematically by Joseph Louis Gay-Lussac in 1802. Other synonyms include the constant-pressure law, the ideal gas law, and the gas expansion law. The law plays a significant role in many fields of science, including chemistry, physics, and engineering. Its applications range from gas-powered engines to everyday household appliances, such as refrigerators and air conditioners.