an enclosed chamber in which heat is produced to heat buildings, destroy refuse, smelt or refine ores, etc.
"The old coal furnace was installed specifically to keep the factory floor warm during winter."
An industrial heating device, e.g. for smelting metal or baking ceramics.
"The workers monitored the temperature of the furnace to ensure the molten steel remained liquid during casting."
In plain English: A furnace is a machine that heats your home by burning fuel to warm up air for your house.
"The old furnace in our basement needs to be replaced soon because it isn't heating the house properly anymore."
Usage: A furnace is an enclosed chamber that uses fuel to generate intense heat for processes like melting metals or firing pottery. It differs from a stove primarily by its large scale and specialized industrial application rather than household cooking.
To heat in a furnace.
"The blacksmith will soon have to heat the iron bar in the furnace before he can forge it into a sword."
The word furnace entered English from the Old French fornais, which itself came from the Latin fornāx. Originally referring to a kiln or oven used in baking and pottery, it retained this core meaning as it traveled through Middle English into modern usage.