limescale

This term refers specifically to the mineral buildup caused by hard water. It carries a negative connotation of neglect or poor maintenance, often associated with domestic chores and the degradation of household appliances.

As an uncountable noun, it describes a mass of material rather than individual units. It is never used in the plural form; instead, quantities are described using partitive phrases such as "a layer of limescale" or "a buildup of limescale."