- a noun denoting something that cannot be counted (e.g. a substance or quality), in English usually a noun which lacks a plural in ordinary usage and is not used with the indefinite article, e.g. china, happiness.；a noun denoting something that normally cannot be counted but that may be countable when it refers to different units or types, e.g. coffee (I drank some coffee, I ordered two coffees).
noun: mass noun, plural noun: mass nouns