There are several synonyms for the term "nuclear submarine" that are used interchangeably in military and technical contexts. One frequently used term is "atomic submarine," which refers to a submersible vessel that is powered by a nuclear reactor. Another synonym is "nuclear-powered submarine," which emphasizes the power source of the vessel. A third equivalent term is "nuclear sub," which is a common shorthand used in informal conversations and media reporting. Regardless of the specific terminology used, the primary characteristic of a nuclear submarine is that it relies on a nuclear propulsion system to operate underwater for extended periods of time.