In the English language, nouns are inflected for grammatical number—that is, singular or plural. This article discusses the variety of ways in which English nouns form their plurals. Phonetic transcriptions, given inside slashes, are in SAMPA notation.
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Most nouns form the plural by adding -s to the singular form (see exceptions below). This is pronounced /z/ except when the preceding sound is a voiceless consonant (see phonation), in which case it is pronounced /s/. Examples:
boy boys girl girls cat cats chair chairs
Where a noun ends in a sibilant sound—such as s, sh, x, soft ch—the plural is formed by adding es (also pronounced as z with a neutral vowel sound or short i):
glass glasses dish dishes witch witches
Phonetically, these rules are sufficient to describe most English plurals. However, there are several complications in spelling.
The -oes rule: most nouns ending in o preceded by a consonant also form their plurals by adding -es (pronounced /z/):
hero heroes potato potatoes volcano volcanoes
The -ies rule: nouns ending in a y preceded by a consonant drop the y and add -ies (pronounced /:iz/):
cherry cherries lady ladies
Note, however, that proper nouns (particularly those for people or places) ending in a y preceded by a consonant form their plurals regularly:
Harry Harrys (as in There are three Harrys in our office) Germany Germanys (as in The two Germanys were unified in 1990)
This does not apply to words that are merely capitalised common nouns:
P&O Ferries (from ferry)
A few common nouns ending in a y preceded by a consonant form their plurals regularly:
henry henrys zloty zlotys
Many nouns of Italian or Spanish origin are exceptions to this rule:
canto cantos grotto grottos piano pianos portico porticos quarto quartos solo solos
Most nouns ending in f or fe form their plurals by changing the f into a v and adding es:
calf calves half halves wolf wolves wharf wharves
Some just add an s:
proof proofs muff muffs
Some can do either:
dwarf dwarfs / dwarves hoof hoofs / hooves staff staffs / staves turf turfs / turves (latter rare) roof roofs / rooves / roovis (latter two archaic)
There are many other less regular ways of forming plurals. While they may seem quirky, they usually stem from older forms of English or from foreign borrowings.
The plural of a few Germanic nouns can also be formed from the singular by adding n or en:
ox oxen eye eyen (Rare, found in some regional dialects) shoe shoon (Also rare/obsolete)
The word box, referring to a computer, is semi-humorously pluralized boxen in the Leet dialect. Multiple Vax computers, likewise, are sometimes called Vaxen.
The plural is sometimes formed by simply changing the vowel sound of the singular, in a process called umlaut (these are sometimes called mutated plurals):
foot feet goose geese louse lice man men mouse mice tooth teeth woman women
Some nouns have singular and plural alike:
sheep deer cod series trout
Because English includes words from so many ancestral languages, as well as many loanwords from Classical Greek and Latin and other modern languages, there are many other forms of plurals. Such nouns often retain their original plurals, at least for some time after they are introduced. In some cases both forms are still vying for attention: for example, for a librarian, the plural of appendix is appendices (following the original language); for physicians, however, the plural of appendix is appendixes. Likewise, an electrician works with antennas and an entomologist deals with antennae. The "correct" form is the one that sounds better in context, or that people in the field use.
Correctly formed Latin plurals are the most acceptable, and indeed are often required, in academic and scientific contexts. In common usage, back-formed plurals are sometimes preferred. (See below for another kind of back-formed plural.)
formula formulae / formulas alumna alumnae
vertex vertices index indices / indexes
axis axes testis testes crisis crises
phenomenon phenomena (more below) criterion criteria automaton automata polyhedron polyhedra
addendum addenda memorandum memoranda / memorandums medium media
radius radii alumnus alumni viscus viscera virus viruses corpus corpora
Note: See article on the Plural of virus.
stigma stigmata stoma stomata
Though some take s more commonly:
schema schemata / schemas dogma dogmata / dogmas
cactus cactuses / cacti hippopotamus hippopotamuses / hippopotami octopus octopuses / octopi platypus platypuses rhinoceros rhinoceroses / rhinoceri
The Greek plural for words ending in -pus meaning "foot", is podes, but this plural is not used in English.
beau beaux chateau chateaux
cherub cherubim / cherubs seraph seraphim / seraphs matzoh matzot / matzos
kimono kimono samurai samurai otaku otaku
Note: kimonos, following the French model, is now generally accepted in English.
Nouns from languages that have donated few words to English, and that are spoken by relatively few English-speakers, generally form plurals as if they were native English words:
canoe canoes kayak kayaks igloo igloos cwm cwms (Welsh valley)
Some words of foreign origin are much better known in the plural; usage of the proper singular may be considered pedantic or actually incorrect by some speakers. In common usage, the proper plural is considered the singular form. Back-formation has usually resulted in a regularized plural.
Proper singular Proper plural/ Common plural
common singular
candelabrum candelabra candelabras
datum data data (mass noun)
agendum agenda agendas / (less common) agendae
graffito graffiti graffiti (mass noun)
insigne insignia insignias
alga algae algae / algaes
opus opera operas
viscus viscera (singular not in common usage)
phalanx phalanges
Note: A single piece of data is often referred to as a data point. A military phalanx is pluralized phalanxes. The phalanges as body parts (fingers and toes) are rarely referred to in the singular.
A related phenomenon is the confusion of a foreign plural for its singular form:
phenomenon phenomena criterion criteria symposium symposia
Plurals for the names of numbers differ according to how they are used. Such words include dozen, hundred, thousand, million, and so forth. The following examples apply to all of these.
Some nouns have no singular form:
annals billiards cattle measles nuptials thanks tidings victuals / vittles
Note, however, that billiard as a singular is used as a number in some versions of British English for 1015 (others will call this a thousand billion or quadrillion), but when speaking of the table game, only exists as plural. These words do have non-noun forms that do not end in s. For example, thank you or billiard ball.
Neither do some names of things having two parts:
scissors trousers tweezers pants
Note, however, that these words are interchangeable with a pair of scissors, a pair of trousers, and so forth. Nor are scissor, trouser, tweezer, or pant the names of the individual parts. However, the fashion industry frequently calls a single pair of pants a pant; this is a back-formation. (See below for another kind of back-formed plural.)
Some words in which the modifier follows the noun form the plural inside the word or phrase, particularly legal terms from French:
attorney general attorneys general son-in-law sons-in-law court martial courts martial armful armsful / armfuls (the latter is preferred today) governor-general governors-general Knight Hospitaller Knights Hospitallers agent provocateur agents provocateurs
It is common in informal speech to pluralise the last word in the usual way, but in edited prose, the forms given are preferred.
Non-countable, or "mass" nouns do not represent distinct objects, so the singular and plural semantics do not apply in the same way. Some examples:
goodness idleness wisdom deceit honesty freshness
chemistry geometry surgery biometrics mechanics optics blues (music)
antimony gold oxygen equipment furniture specie distress sand water air informations
Some mass nouns can be pluralized, but the meaning thereof may change slightly. For example, when I have two pieces of sand, I do not have two sands; I have sand. There is more sand in your pile, not more sands. But there could be many "sands of Africa" - either many distinct stretches of sand, or distinct types of sand of interest to geologists or builders, or simply the allusive sands of Africa.
It is rare to pluralize furniture in this way. Nor would information be so treated, except in the case of criminal informations, which are prosecutor's briefs similar to indictments.
There is only one class of atoms called oxygen, but there are several isotopes of oxygen, which might be referred to as different oxygens. In casual speech, oxygen might be used as shorthand for "oxygen atoms", but in this case it is not a mass noun, so it is entirely sensible to refer to multiple oxygens in the same molecule.
One would interpret "Bob's wisdoms" as various pieces of Bob's wisdom (that is, pieces of advice), deceits as a series of instances of deceitful behavior, and the different idlenesses of the worker as plural distinct manifestations of the mass concept of idleness (or as different types of idleness, "bone lazy" versus "no work to do").
Some nouns have two plurals, one used to refer to a number of things considered individually, the other to refer to a number of things collectively. In some cases, one of the two is nowadays archaic or dialectal.
brother brothers brethren cannon cannons cannon child children childer* cow cows kine* die dice dies fish fish fishes* penny pennies pence* sow sows swine pig pigs swine iris iris irises* cloth cloths clothes*
A final odd case is person. The word people is usually treated as the suppletive plural of person (one person, many people). However, in legal and other formal contexts, the plural of person is persons; furthermore, people can also be a singular noun with its own plural (for example, "We are many persons, from many peoples").
Symbols and abbreviations whose plural would be ambiguous if only an s were added are pluralized by adding 's.
mind your p's and q's
Regular words and non-ambiguous abbreviations (like PCs or ICBMs) should be pluralized in the normal way, not with an apostrophe, lest they be confused with the possessive.
Linguist Steven Pinker, in his book, The Language Instinct discusses what he calls "headless words", that is, words like low-life and Red Sox where the life and sox are not being used in their ordinary senses. Thus, more than one low-life is low-lifes and a single member of the Boston baseball team is a Red Sox. Other examples include the ice-hockey Maple Leafs, not Maple Leaves, sabertooth and sabertooths, flatfoot and flatfoots, tenderfoot and tenderfoots, still life and still lifes. Thus, the plural of mongoose is mongooses.
The computer mouse is often pluralized mouses, although, in this case, mice is just as common because of the physical similarity between the input device and the rodent.
Some words have started out with unusually formed singulars and plurals, but more "normal" singular-plural pairs have resulted. For an example from the vegetable world, pease was the singular and peasen the plural, but over the centuries, first pease became the plural and pea the singular, and finally the plural was altered to peas. Similarly, termites and primates were the three-syllable plurals of termes and primas, respectively, but these singulars were lost, the plurals given two syllables, and now we have termite and termites and primate and primates. Syringe is a back formation from syringes, itself the plural of syrinx, a musical instrument. Cherry is from Norman French cherise. Finally, phases was once the plural of phasis, but the singular is now phase.
Kudos is a singular Greek word meaning praise, but the same process may be happening to it. At present, kudo is an error, however.
There are several different rules for this.
In discussing peoples whose demonym takes -man or -woman, there are two options: pluralize to -men or -women if referring to individuals, and use the root alone if referring to the whole nation.
Englishman Englishmen the English
Frenchwoman Frenchwomen the French
Dutchman or Dutch people the Dutch
Dutchwoman
This also applies to the Irish and the Welsh. One can say "a Scots(wo)man" or "a Scot", "Scots(wo)men", "Scottish people", or "Scots," and "the Scottish" or "the Scots". (Scotch is a drink.)
Several peoples have names that are simple nouns and can be pluralized:
Dane Danes the Danes (or) the Danish
Finn Finns the Finns (or) the Finnish
Swede Swedes the Swedes (or) the Swedish
Spaniard Spaniards the Spaniards (or) the Spanish
(much more common)
Names of peoples that end in -ese take no plural:
Chinese Chinese the Chinese
(or Chinese people)
Neither do Swiss or Quebecois.
Most names for American Aboriginal groups are not pluralized:
Ojibwa Ojibwa Iroquois Iroquois Blood Blood Mi'kmaq Mi'kmaq
Some exceptions include Crees, Mohawks, Hurons, Algonquins, Chippewas, Oneidas, Aztecs. Note also:
Inuk Inuit
Most other peoples of the world are pluralized using the normal English rules.