a noun such as ‘soap' that is usually uncountable but is also used with ‘a' or ‘an', or in the plural, to talk about different types of something. For example the noun ‘soap' in ‘Wash your hands with soap and water' is uncountable, while in ‘You should choose a mild soap' and ‘Some soaps are very strongly perfumed', ‘soap' is countable. A mass noun is used in both these ways. 物质名词(指通常不可数但可以当成复数使用或与不定代词连用的名词,如soap) Synonyms and related words