- a chemical compound added to hard water to soften it, as by precipitating out the minerals
- a tank or other container in which water is filtered through any of various chemicals or ion exchange media for softening
water softenerwater softener
- A substance used to reduce the concentration of calcium and magnesium ions in water, as to improve the lathering action of soaps and other cleansing agents.
- A device that monitors and reduces the amount of such ions in a water supply.
(plural water softeners)