A gasholder is a large cylindrical container used to store natural gas at a constant pressure. Although "gasholder" is the most commonly used term for the container, there are several other synonyms that can be used. Some of the most prevalent synonyms include gasometer, gas tank, gas holder, and gasometer tank. Other, less commonly used synonyms include gas bell, gas sphere, and gas dome. While all of these words describe essentially the same thing, the term "gasholder" has become the most familiar term in the modern era. Regardless of the synonym used, gasholders have played an important role in facilitating the widespread use of natural gas as an energy source.