Inlinguistics, amass noun,uncountable noun,non-count noun,uncount noun, or justuncountable, is anoun with thesyntactic property that any part and quantity^{[Note 1]} of it is treated as an undifferentiated unit, rather than as something with discrete elements. Uncountable nouns are distinguished fromcount nouns.

Given that differentlanguages have differentgrammatical features, the actual test for which nouns are mass nouns may vary between languages. InEnglish, mass nouns are characterized by the impossibility of being directly modified by anumeral without specifying aunit of measurement and by the impossibility of being combined with anindefinite article (a oran). 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", though note the different quantifiers "much" and "many").

Mass nouns have no concept ofsingular andplural, although in English they take singularverb forms. However, many mass nouns in English can beconverted to count nouns, which can then be used in the plural to denote (for instance) more than one instance or variety of a certain sort of entity – for example, "Many cleaning agents today are technically not soaps [i.e. types of soap], but detergents," or "I drank about three beers [i.e. bottles or glasses of beer]".

Some nouns can be used indifferently as mass or count nouns,e.g.,three cabbages orthree heads of cabbage;three ropes orthree lengths of rope. Some have differentsenses as mass and count nouns:paper is a mass noun as a material (three reams of paper,one sheet of paper), but a count noun as a unit of writing ("the students passed in their papers").

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. But there are many exceptions: the mass/count distinction is a property of theterms, not their referents. For example, the same set of chairs can be referred to as "seven chairs" (count) and as "furniture" (mass); the Middle English mass nounpease has become the count nounpea bymorphological reanalysis; "vegetables" are a plural count form, while the British English slang synonym "veg" is a mass noun.

In languages that have apartitive case, the distinction is explicit and mandatory. For example, inFinnish,join vettä, "I drank (some) water", the wordvesi, "water", is in the partitive case. The related sentencejoin veden, "I drank (the) water", using theaccusative case instead, assumes that there was a specific countable portion of water that was completely drunk.

The work of logicians likeGodehard Link andManfred Krifka established that the mass/count distinction can be given a precise, mathematical definition in terms ofquantization andcumulativity.^[1]

An expressionP hascumulative reference if and only if^[2][3] for anyX andY:

• IfX can be described asP andY can be described asP, as well, then the sum ofX andY can also be described asP.

In more formal terms (Krifka 1998):

${\displaystyle \mathrm{\forall }X\subseteq U_p[{\mathrm{C}\mathrm{U}\mathrm{M}}_p(X)\iff \mathrm{\exists }x,y[X(x)\wedge X(y)\wedge \mathrm{\neg }(x=y)]\wedge \mathrm{\forall }x,y[X(x)\wedge X(y)\Rightarrow X(x\oplus y)]]}$

which may be read as:X is cumulative if there exists at least one pair x,y, wherex andy are distinct, and both have the propertyX, and if for all possible pairsx andy fitting that description,X is a property of the sum ofx andy.^[4]

Consider, for examplecutlery: If one collection of cutlery is combined with another, we still have "cutlery." Similarly, if water is added to water, we still have "water." But if a chair is added to another, we do not have "a chair", but rather two chairs. Thus the nouns "cutlery" and "water" have cumulative reference, while the expression "a chair" does not. The expression "chairs", however, does, suggesting that the generalization is not actually specific to the mass-count distinction. As many have noted, it is possible to provide an alternative analysis, by which mass nouns and plural count nouns are assigned a similar semantics, as distinct from that of singular count nouns.^[5]

An expressionP hasquantized reference if and only if, for any X:

• IfX can be described asP, then no proper part ofX can be described asP.

This can be seen to hold in the case of the nounhouse: no proper part ofa house, for example the bathroom, or the entrance door, is itself a house. Similarly, no proper part ofa man, say his index finger, or his knee, can be described asa man. Hence,house andman have quantized reference. However, collections ofcutlery do have proper parts that can themselves be described ascutlery. Hencecutlery does not have quantized reference. Notice again that this is probably not a fact about mass-count syntax, but about prototypical examples, since many singular count nouns have referents whose proper parts can be described by the same term. Examples include divisible count nouns like "rope", "string", "stone", "tile", etc.^[5]

Some expressions are neither quantized nor cumulative. Examples of this includecollective nouns likecommittee. A committee may well contain a proper part which is itself a committee. Hence this expression is not quantized. It is not cumulative, either: the sum of two separate committees is not necessarily acommittee. In terms of the mass/count distinction,committee behaves like a count noun. By some accounts, these examples are taken to indicate that the best characterization of mass nouns is that they arecumulative nouns. On such accounts, count nouns should then be characterized asnon-cumulative nouns: this characterization correctly groupscommittee together with the count nouns. If, instead, we had chosen to characterize count nouns asquantized nouns, and mass nouns asnon-quantized ones, then we would (incorrectly) be led to expectcommittee to be a mass noun. However, as noted above, such a characterization fails to explain many central phenomena of the mass-count distinction.

Many Englishnouns can be used in either mass or count syntax, and in these cases, they take on cumulative reference when used as mass nouns. For example, one may say that "there'sapple in this sauce", and thenapple has cumulative reference, and, hence, is used as a mass noun. The names of animals, such as "chicken", "fox" or "lamb" are count when referring to the animals themselves, but are mass when referring to their meat, fur, or other substances produced by them. (e.g., "I'm cooking chicken tonight" or "This coat is made of fox.") Conversely, "fire" is frequently used as a mass noun, but "a fire" refers to a discrete entity. Substance terms like "water" which are frequently used as mass nouns, can be used as count nouns to denote arbitrary units of a substance ("Twowaters, please") or of several types/varieties ("waters of the world").^[6]

• "I'll have acup ofcoffee." (count noun with classifier)
• "I'll have twocoffees." (count noun without classifier)
• "I'll havecoffee." (plain mass noun)
• "I'll havesome coffee." (mass noun with determiner)
• "I'll havetoo much coffee." (mass noun with modified determiner)

One may say that mass nouns that are used as count nouns are "countified" and that count ones that are used as mass nouns are "massified". However, this may confuse syntax and semantics, by presupposing that words which denote substances are mass nouns by default. It has been suggested nouns do not have a lexical specification for mass-count status, and instead are specified as such only when used in a sentence.^[7]

Nouns differ in the extent to which they can be used flexibly, depending largely on their meanings and the context of use. For example, the count noun "house" is difficult to use as mass (though clearly possible), and the mass noun "cutlery" is most frequently used as mass, despite the fact that it denotes objects, and has count equivalents in other languages:

• Incorrect: *There is house on the road. (Incorrect even if a catastrophe is considered)
• Incorrect: *There is a cutlery on the table. (Incorrect even if just one fork is on the table)
• Correct: You got a lot of house for your money since the recession.
• Correct: Spanish cutlery is my favorite. (type / kind reading)

In some languages, such asChinese andJapanese, it has been claimed by some that all nouns are effectively mass nouns, requiring ameasure word to be quantified.^[8]

Somequantifiers can be used with both mass nouns and count nouns, includingall,no, andsome. Others cannot:few,many,those, and numbers (one) are used with count nouns;little andmuch with mass nouns. This also applies to phrasal quantifiers. For example,an amount of is for mass nouns,a number of is for count nouns, anda lot of can be used with both types.

Whereasmore andmost are uncontroversially thecomparative andsuperlative of bothmuch andmany, a controversial prescription is forfew andlittle to have differing comparative and superlative forms (fewer,fewest andless,least), but use ofless andleast with count nouns has always been common (seeFewer versus less).^[9] This criticism only dates back to 1770, but the criticized usage dates back toOld English.^[9]

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There is often confusion about the two different concepts ofcollective noun andmass noun. Generally, collective nouns such asgroup, family, andcommittee are not mass nouns but are rather a special subset ofcount nouns. However, the term "collective noun" is often used to mean "mass noun" (even in some dictionaries) because users conflate two different kinds of verb number invariability: (a) that seen with mass nouns such as "water" or "furniture", with which only singular verb forms are used because the constituent matter isgrammatically indivisible (although it may ["water"] or may not ["furniture"] beetically indivisible); and (b) that seen with collective nouns, which is the result of themetonymical shift between the group and its (both grammatically and etically) discrete constituents.

Some words, including "mathematics" and "physics", have developed true mass-noun senses despite having grown from count-noun roots.

• Plurale tantum – Noun that appears only in the plural form

• The Mavens Word of the Day: less/fewer
• Semantic Archives: Mass nouns, count nouns and non-count nouns
• F.J. Pelletier L.K. Schubert (2001) Mass Expressions in D. Gabbay & F. Guenthner (eds) Handbook of Philosophical Logic, Vol. 10
• "Conceptual Categories and Linguistic Categories VIII: Nouns and Individuation", summer 2011, byBeth Levin at web.stanford.edu

• Nouns by type
• Grammatical number
• Syntax–semantics interface

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