In many languages, such as English, number is obligatorily expressed in every grammatical context; in other languages, however, number expression is limited to certain classes of nouns, such as animates or referentially prominent nouns (as with proximate forms in most Algonquian languages, opposed to referentially less prominent obviative forms).
A very common situation is for plural number to not be marked if there is any other overt indication of number, as for example in Hungarian: virág "flower"; virágok "flowers"; hat virág "six flowers".
In many languages, verbs are conjugated for number. Using French as an example, one says je vois (I see), but nous voyons (we see). The verb voir (to see) changes from vois in the first person singular to voyons in the plural. In everyday English, this often happens in the third person (she sees, they see), but not in other grammatical persons, except with the verb to be.
Adjectives often agree with the number of the noun they modify. For example, in French, one says un grand arbre [œ̃ gʀɑ̃t aʀbʀ] "a tall tree", but deux grands arbres [dø gʀɑ̃z aʀbʀ] "two tall trees". The singular adjective grand becomes grands in the plural, unlike English "tall", which remains unchanged.
Other determiners may agree with number. In English, the demonstratives "this", "that" change to "these", "those" in the plural, and the indefinite article "a", "an" is either omitted or changes to "some". In French and German, the definite articles have gender distinctions in the singular but not the plural. In Spanish and Portuguese, both definite and indefinite articles are inflected for gender and number, e.g. Portuguese o, a "the" (singular, masc./fem.), os, as "the" (plural, masc./fem.); um, uma "a(n)" (singular, masc./fem.), uns, umas "some" (plural, masc./fem.)
In the Finnish sentence Yöt ovat pimeitä "Nights are dark", each word referring to the plural noun yöt "nights" ("night" = yö) is pluralized (night-PL is-PL dark-PL-partitive).
Sometimes, grammatical number will not represent the actual quantity. For example, in Ancient Greek neuter plurals took a singular verb. The plural form of a pronoun may also be applied to a single individual as a sign of importance, respect or generality, as in the pluralis majestatis, the T-V distinction, and the generic "you", found in many languages, or, in English, when using the singular "they" for gender-neutrality.
A collective noun is a word that designates a group of objects or beings regarded as a whole, such as "flock", "team", or "corporation". Although many languages treat collective nouns as singular, in others they may be interpreted as plural. In British English, phrases such as the committee are meeting are common (the so-called agreement in sensu "in meaning", that is, with the meaning of a noun, rather than with its form). The use of this type of construction varies with dialect and level of formality.
In most languages with grammatical number, nouns, and sometimes other parts of speech, have two forms, the singular, for one instance of a concept, and the plural, for more than one instance. Usually, the singular is the unmarked form of a word, and the plural is obtained by inflecting the singular. This is the case in English: car/cars, box/boxes, man/men. There may be exceptional nouns whose plural is identical to the singular: one fish / two fish.
Some languages differentiate between a basic form, the collective, which is indifferent in respect to number, and a more complicated derived form for single entities, the singulative, for example Japanese and some Brythonic languages. A rough example in English is "snowflake", which may be considered a singulative form of "snow" (although English has no productive process of forming singulative nouns, and no singulative modifiers). In other languages, singulatives can be productively formed from collective nouns; e.g. Standard Arabic حجر ḥajar "stone" → حجرة ḥajarā "(individual) stone", بقر baqar "cattle" → بقرة baqarā "(single) cow"
The distinction between a "singular" number (one) and a "plural" number (more than one) found in English is not the only possible classification. Another one is "singular" (one), "dual" (two) and "plural" (more than two). Dual number existed in Proto-Indo-European, persisted in many of the now extinct ancient Indo-European languages that descended from it—Sanskrit, Ancient Greek and Gothic for example—and can still be found in a few modern Indo-European languages such as Icelandic and Slovene language. Many more modern Indo-European languages show residual traces of the dual, as in the English distinctions both versus all and better versus best.
Many Semitic languages also have dual number.
The trial number is a grammatical number referring to 'three items', in contrast to 'singular' (one item), 'dual' (two items), and 'plural' (four or more items). Tolomako, Lihir and Tok Pisin (though only in its pronouns) have trial number.
There is a hierarchy between number categories: No language distinguishes a trial unless having a dual, and no language has dual without a plural (Greenberg 1972).
Some languages, such as Latvian, have a nullar form, used for nouns that refer to zero items. Other languages use either the singular or the plural form for zero. English, along with the other Germanic languages and most Romance languages, uses the plural. French normally uses the singular, instead.
Distributive plural number, for many instances viewed as independent individuals (e.g. in Navajo).
In most languages, the singular is formally unmarked, whereas the plural is marked in some way. Other languages, most notably the Bantu languages, mark both the singular and the plural, for instance Swahili (see example above). The third logical possibility, rarely found in languages, is unmarked plural contrasting with marked singular.
Elements marking number may appear on nouns and pronouns in dependent-marking languages or on verbs and adjectives in head-marking languages.
| English (dependent-marking) | Western Apache (head-marking) |
| Paul is teaching the cowboy. | Paul idilohí yiłch’ígó’aah. |
| Paul is teaching the cowboys. | Paul idilohí yiłch’ídagó’aah. |
In the English sentence above, the plural suffix -s is added to the noun cowboy. In the Western Apache, a head-marking language, equivalent, a plural prefix da- is added to the verb yiłch’ígó’aah "he is teaching him", resulting in yiłch’ídagó’aah "he is teaching them" while noun idilohí "cowboy" is unmarked for number.
Plurality is sometimes marked by a specialized number particle (or number word). This is frequent in Australian and Austronesian languages. An example from Tagalog is the word mga: compare bahay "house" with mga bahay "houses". In Kapampangan, certain nouns optionally denote plurality by secondary stress: ing laláki "man" and ing babái "woman" become ding láláki "men" and ding bábái "women".
· Beard, R. (1992) Number. In W. Bright (ed.) International Encyclopedia of Linguistics.
· Corbett, G. (2000). Number. Cambridge University Press.
· Greenberg, Joseph H. (1972) Numeral classifiers and substantival number: Problems in the genesis of a linguistic type. Working Papers on Language Universals (Stanford University) 9. 1-39.
· Laycock, Henry. (2005) 'Mass nouns, Count nouns and Non-count nouns' Encyclopedia of Language and Linguistics. Oxford: Elsevier.
· Laycock, Henry. (2006) Words without Objects. Oxford: Clarendon Press.
· Merrifield, William (1959). Classification of Kiowa nouns. International Journal of American Linguistics, 25, 269-271.
· Mithun, Marianne (1999). The languages of native North America (pp. 81-82, 444-445). Cambridge University Press, ISBN 0-521-23228-7.
· Sprott, Robert (1992). Jemez syntax. (Doctoral dissertation, University of Chicago, USA).
· Sten, Holgar (1949) Le nombre grammatical. (Travaux du Cercle Linguistique de Copenhague, 4.) Copenhagen: Munksgaard.
· Watkins, Laurel J.; & McKenzie, Parker. (1984). A grammar of Kiowa. Studies in the anthropology of North American Indians. Lincoln: University of Nebraska Press. ISBN 0-8032-4727-3.
· Weigel, William F. (1993). Morphosyntactic toggles. Papers from the 29th Regional Meeting of the Chicago Linguistic Society (Vol. 29, pp. 467-478). Chicago: Chicago Linguistic Society.
· Wiese, Heike (2003). Numbers, language, and the human mind. Cambridge University Press, ISBN 0-521-83182-2.
· Wonderly, Gibson, and Kirk (1954). Number in Kiowa: Nouns, demonstratives, and adjectives. International Journal of American Linguistics, 20, 1-7.
· Vinokurova, Nadezhda. 2005. [1] Lexical categories and argument structure : a study with reference to Sakha.] Ph.D. diss. University of Utrecht.
· Davidson, Donald. 1967. The logical form of action sentences. In Nicholas Rescher, ed., The Logic of Decision and Action, Pittsburgh, Pa: University of Pittsburgh Press.
· Parsons, Terence. 1990. Events in the semantics of English: a study in subatomic semantics. Cambridge, Mass.:MIT Press
· Croft, William. 1993. "A noun is a noun is a noun - or is it? Some reflections on the universality of semantics." Proceedings of the Nineteenth Annual Meeting of the Berkeley Linguistics Society, ed. Joshua S. Guenter, Barbara A. Kaiser and Cheryl C. Zoll, 369-80. Berkeley: Berkeley Linguistics Society.