A gas maser is a device that amplifies microwave radiation using the process of stimulated emission. Synonyms for gas maser include molecular maser, atomic maser, and quantum maser. A molecular maser amplifies microwave radiation using molecules as the active medium, while an atomic maser uses atoms. A quantum maser refers to any maser that operates using the principles of quantum mechanics. Other related terms include laser, which amplifies light instead of microwaves, and maser oscillator and amplifiers, which are specific types of maser devices. While gas masers are not as commonly used as other types of amplifiers, they are still important tools in scientific research and industrial applications.