An English plural—that is, the plural form of a singular noun—is most commonly formed by adding an s to the singular form (though it is generally pronounced as a z except after an unvoiced consonant):

boy           boys
girl          girls
cat           cats
table         tables

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.

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

Nouns ending in o preceded by a consonant also form their plurals by adding es:

hero          heroes
potato        potatoes
volcano       volcanoes

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

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

Dwarf is an interesting case: the common form of the plural was dwarfs—as, for example, in Walt Disney's Snow White and the Seven Dwarfs—until J.R.R. Tolkien came along and popularised dwarves. Multiple dwarf stars, or non-mythological short human beings, however, are dwarfs.
  • Staff: in the sense of "a body of employees" the plural is always staffs; otherwise both staffs and staves are acceptable, except in compounds; such as flagstaffs.

  • Nouns ending in y preceded by a consonant change their ending to ies:

    cherry        cherries
    lady          ladies

    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 plural is sometimes formed by simply changing the vowel sound of the singular, in a process called ablaut (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

    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.
    • When modified by a number, the plural is not inflected, that is, has no s added. Hence one hundred, two hundred , etc. For vaguer large numbers, one could say several hundred, but many hundreds.
    • When used alone, or followed by a prepositional phrase, the plural is inflected: dozens of complaints. However, either complaints by the dozen or complaints by the dozens is acceptable.
    • The preposition of is used when speaking of non-specific items identified by pronouns: two hundred of these, three dozen of those. The of is not used for a number of specific items: three hundred oriental rugs. However, if the pronoun is included with the specific item, the of is used: five million of those dollar bills.

    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), but when speaking of the table game, only exists as plural.

    Neither do some names of things having two parts:

    scissors
    trousers
    tweezers
    pants

    Note, however, that the fashion industry frequently calls a single pair of pants a pant; this is a back-formation.

    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

    It is common in non-formal speech to pluralise the last word in the usual way, but in edited prose, the forms given are preferred.

    Some nouns have no plural form:

    • abstract nouns
    goodness            idleness            wisdom

    Note, however, that if Wisdom is used as a title ("Your Wisdom") it is then given a regular plural—Their Wisdoms.

    • non-countable nouns, such as chemical elements and substances:

    antimony            gold                oxygen
    equipment           furniture           specie              distress

    arts and sciences (even those ending in ics are treated as singular)

    chemistry           geometry            surgery
    biometrics          mechanics           optics
    blues (music)

    Specie and species make a fascinating case. Both words come from a Latin word meaning "kind", but they do not form a singular-plural pair; they are separate non-countable nouns. Coins, such as nickels, euros, and cents are specie, but there is no plural. The idea is "payment in kind". And species, the "kinds of living things", is the same in singular and plural.
  • Some names of elements, such as nickel, have plurals in non-chemical uses, as "five nickels to the quarter".
  • Some non-countable substance nouns like "tea" or "wood" have plurals that mean "varieties of..." tea, wood, etc.

  • 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               childer             children
    cow                 cows                kine
    die                 dies                dice
    fish                fishes              fish
    penny               pennies             pence
    sow                 sows                swine
    pig                 pigs                swine 
    iris                iris                irises 
    cloth               cloths              clothes             

    Childer has all but disappeared, but can still be seen in Childermas (Innocents' Day)
  • Kine is still used in rural English dialects
  • Dies is used as the plural for die in the sense of a mould; dice as the plural (and increasingly as the singular) in the sense of a small random number generator
  • Fish: the plural for one species of fish, or caught fish, is fish, but for live fish of many species, or in poetic usage, fishes is used.
  • For multiple plants, say iris, but for multiple blossoms say irises.
  • Clothes refers collectively to all of the cloth covering a person's body.
  • If you have several (British) one-penny pieces you have several pennies; pence is used for an amount of money (which can be made up of a number of coins of different denominations: one penny and one five-penny piece are together worth six pence); penny and pennies are also use to refer to one or more U.S. one-cent pieces

  • 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 are never\ pluralized in this way, nor are abbreviations made from initials without periods, as in PCs and ICBMs.

    Table of contents
    1 More on plurals of English words of foreign origin
    2 Plural to singular by back formation
    3 Names of peoples

    More on plurals of English words of foreign origin

    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 the better in context.

    Correctly formed Latin plurals are the most acceptable, and indeed are often required, in academic and scientific contexts.

    • Final a becomes ae (strictly æ)—or just adds s:

    formula        formulae / formulas

    alumna alumnae

    Final ex becomes ices— or just adds es:

    vertex         vertices
    index          indices / indexes

    Final is becomes es:

    axis           axes
    testis        testes 
    crisis        crises

    Final on becomes a:

    phenomenon     phenomena (more below)
    criterion      criteria
    automaton      automata
    polyhedron     polyhedra

    Final um becomes a – or just adds s

    addendum       addenda
    memorandum     memoranda / memorandums
    medium         media

    Final us becomes i (second declension) or era or ora (third declension)—or just adds es (especially in fourth declension, where it would otherwise be the same as the singular):

    radius         radii
    alumnus        alumni
    viscus         viscera
    virus          viruses
    corpus         corpora

    Note: in Latin, virus has no plural form. Viri and virii are both incorrect.

    • Final ma in nouns of Greek origin add ta:

    stigma        stigmata
    stoma         stomata

    Though some take s more commonly:

    schema        schemata or schemas
    dogma         dogmata or dogmas

    Final us in nouns of Greek origin add es

    cactus         cactuses
    hippopotamus   hippopotamuses
    octopus        octopuses
    platypus       platypuses / platypus
    rhinoceros     rhinoceroses / rhinoceros

    Of course, the Latinate i plural is frequently heard for these words, but it is considered an error of pedantic hypercorrectness that is not generally accepted in formal use despite having made its way into some dictionaries. (The Greek plural for words ending in -pus meaning "foot", is podes, but that plural is not used in English.)

    • Some nouns of French origin add x

    beau           beaux 
    chateau        chateaux

    Nouns of Hebrew language origin add im or ot (generally m/f)—or just s
    Note that ot is pronounced os in the Ashkenazi dialect.

    cherub         cherubim / cherubs
    seraph         seraphim / seraphs
    matzoh         matzot / matzos

    Nouns of Japanese origin have no plural and do not change:

    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, while the singular is hardly ever heard except from the fully precise, and with the plural usually taking a singular verb:

    candelabrum      candelabra
    datum            data
    agendum          agenda 
    graffito         graffiti
    insigne          insignia
    viscus           viscera
    alga             algae
    opus             opera
    phalanx          phalanges

    Insignia is sometimes counted as a singular form with insignias as its plural, but this usage comes across as illiterate to many people. The singular form insigne is now very rare and sounds absurdly pedantic, so the safest bet is to use insignia only as a plural and to substitute a close synonym (such as symbol or emblem) in place of the singular.

    There is an even worse problem with the word data. Although its use as a mass noun is gaining acceptance, to many people it sounds wrong whether used as a singular or as a plural! "The data is" seems jarringly incorrect but "the data are" seems equally jarringly pedantic. The safe way is to use the word only if it would be correct whether singular or plural (for example, "we checked the data"), and to substitute a synonym in other contexts (for example, "the figures are" or "the information is").

    A related phenomenon is the confusion of a foreign plural for its singular form:

    phenomenon        phenomena
    criterion         criteria
    symposium         symposia

    Mouses is sometimes seen for computer pointing devices, although mice is probably more common.

    Plural to singular by back formation

    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.


    Names of peoples

    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)

    The term spaniard is most commonly used to refer to a Spanish-speaking inhabitant of Spain (as opposed to a Spanish speaker in another Spanish-speaking country).

    Names of peoples that end in -ese take no plural:

    Chinese          Chinese           the Chinese
                       (or Chinese people)

    Neither do Swiss and 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.