Uncountable noun

In linguistics, a mass noun, uncountable noun, or non-count noun is a noun with the syntactic property that any quantity of it is treated as an undifferentiated unit, rather than as something with discrete subsets. Non-count nouns are distinguished from count nouns.

Given that different languages have different grammatical features, the actual test for which nouns are mass nouns may vary between languages. In English, mass nouns are characterized by the fact that they cannot be directly modified by a numeral without specifying a unit of measurement, and that they cannot combine with an indefinite article (a or an). Thus, the mass noun "water" is quantified as "20 litres of water" while the count noun "chair" is quantified as "20 chairs". However, both mass and count nouns can be quantified in relative terms without unit specification (e.g., "so much water," "so many chairs").

Some mass nouns can be used in English in the plural to mean "more than one instance (or example) of a certain sort of entity"—for example, "Many cleaning agents today are technically not soaps, but detergents." In such cases they no longer play the role of mass nouns, but (syntactically) they are treated as count nouns.

Some nouns have both a mass sense and a count sense (for example, paper).

In English (and in many other languages), there is a tendency for nouns referring to liquids (water, juice), powders (sugar, sand), or substances (metal, wood) to be used in mass syntax, and for nouns referring to objects or people to be count nouns. This is not a hard-and-fast rule, however; mass nouns such as furniture and cutlery, which represent more easily quantified objects, show that the mass/count distinction should be thought of as a property of the terms themselves, rather than as a property of their referents. For example, the same set of chairs can be referred to as "seven chairs" and as "furniture"; although both chair and furniture are referring to the same thing, the former is a count noun and the latter a mass noun. The Middle English mass noun pease has become the count noun pea by morphological reanalysis.

For another illustration of the principle that the count/non-count distinction lies not in an object but rather in the expression that refers to it, consider the English words "fruit" and "vegetables". The objects that these words describe are, objectively speaking, similar (that is, they're all edible plant parts); yet the word "fruit" is (usually) non-count, whereas "vegetables" is a plural count form. One can see that the difference is in the language, not in the reality of the objects. Meanwhile, German has a general word for "vegetables" that, like English "fruit", is (usually) non-count: das Gemüse. British English has a slang word for "vegetables" that acts the same way: "veg" [rhymes with "edge"].

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