Plurale tantum
A ; ) 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 that denote objects that occur or function as pairs or sets, such as spectacles, trousers, pants, scissors, clothes, or genitals. Other examples are for collections that, like alms, cannot conceivably be singular. Other examples include suds, jeans, outskirts, odds, riches, goods, news, gallows, surroundings, thanks, and heroics.
In some languages, pluralia tantum refer to points or periods of time, or to events, or to liquids.
A bilingual example is the Latin word fasces that 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 press" and "scissor kick" contain the singular form, but it is considered nonstandard to say "a trouser" or "a scissor" on its 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 that 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 " 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. Others like "nothingness" or "emptiness" refer to logical states of absence that can't sensibly be quantified at all, hence are not usefully "mass nouns" but are still singulare tantum.
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, while in Spanish un pantalón and unos pantalones are both valid ways to refer to a single garment. Additionally, in German, the term "Jeans" which is borrowed from English, is rendered singular feminine as die Jeans in accordance with the singular feminine word die Hose meaning "trousers".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.
The Yiddish word kreplach is a well known example of a plurale tantum that is also plural only in other languages into which it is borrowed, 'one of the kreplach' would be איינער פון די קרעפּלאַך.
The Welsh nefoedd, 'heaven', is the plural of nef, which is no longer part of the spoken language. Nefoedd is now used with the singular meaning of 'heaven' and plural of 'heavens'.
In Hebrew, a few words that indicate an action establishing a new relationship between two persons, are indicated by the plural form only: אירוסין, נישואין, קידושין, גירושין, פיטורין, and likewise.