A plurale tantum is a noun that appears only in the plural form and does not have a singular variant for referring to a single object. In a less strict usage of the term, it can also refer to nouns whose singular form is rarely used. In English, pluralia tantum are often words which denote objects that occur or function as pairs or sets, such as spectacles, trousers, pants, scissors, clothes, or genitals. Other examples are for collections which, like alms and feces/faeces, cannot conceivably be singular. Other examples include , jeans, outskirts, odds, riches, surroundings, thanks, and heroics. In some languages, pluralia tantum refer to points or periods of time or to events. In some cases there is no obvious semantic reason for a particular noun to be plurale tantum. The Hebrew מַיִם 'water', Chichewa madzí 'water', Dutch hersenen 'brain', Swedish pengar and Russian den'gi 'money' are pluralia tantum. A bilingual example is the Latin word fasces, which was brought into English; when referring to the symbol of authority, it is a plurale tantum noun in both languages.
English usage
In English, some plurale tantum nouns have a singular form, used only attributively. Phrases such as "trouser presses" and "scissor kick" contain the singular form, but it is considered nonstandard to say "a trouser" or "a scissor" on their own. That accords with the strong preference for singular nouns in attributive positions in English, but some words are used in the plural form even as attributive nouns, such as "clothes peg", "glasses case" – notwithstanding "spectacle case" and "eyeglass case". In English, a word may have many definitions only some of which are pluralia tantum. The word "glasses" is plurale tantum. In contrast, the word "glass"— either a container for drinks or a vitreous substance — may be singular or plural. Some words, such as "brain" and "intestine", can be used as either plurale tantum nouns or count nouns.
Singulare tantum
The term for a noun which appears only in the singular form is singulare tantum, such as the English words information, dust, and wealth. Singulare tantum is defined by the Shorter Oxford English Dictionary as "Gram. A word having only a singular form; esp. a non-count noun." Such nouns may refer to a unique singular object, but more often than not, they refer to uncountable nouns, either mass nouns or collective nouns. Given that they do not have a number distinction, they may appear as singulare tantum in one language but as plurale tantum in another. Compare English water to the Hebrew plurale tantum, מַיִם. In English, such words are almost always mass nouns. Some uncountable nouns can be alternatively used as count nouns when meaning "a type of", and the plural means "more than one type of". For example, strength is uncountable in Strength is power, but it can be used as a countable noun to mean an instance of strength, as in My strengths are in physics and chemistry. Some words, especially proper nouns such as the name of an individual, are nearly always in the singular form because there is only one example of what that noun means.
Usage in other languages
Pluralia tantum vary arbitrarily between languages. For example, in Swedish, a pair of scissors is just en sax, not a plurale tantum; similarly, in French, a pair of trousers is 'un pantalon'. In some other languages, rather than quantifying a plurale tantum noun with a measure word, special numeral forms are used in such cases. In Polish, for example, "one pair of eyeglasses" is expressed as either jedne okulary or jedna para okularów. For larger quantities, "collective numeral" forms are available: troje drzwi, pięcioro skrzypiec. Compare them to the ordinary numeral forms found in Polish: trzy filmy/pięć filmów The Russian деньги originally had a singular, denga, which meant a copper coin worth half a kopeck.
