A furnace is a device used to generate heat through combustion or electric energy. It's used in homes for central heating and hot water, as well as in industrial settings for various processes such as smelting, drying, and heating. There are many synonyms for the word 'furnace', such as heater, stove, kiln, boiler, incinerator, firebox, heating system, and hearth. Each of these words has a slightly different meaning, but they all refer to a source of heat. Some, like kiln and boiler, describe specific types of furnaces that are used in particular circumstances. Whether you're talking about your home heating system or an industrial process, one of these synonyms might be just what you need to describe your furnace.