English plural

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     
 clothes             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
 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 

• 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.
• 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.

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. 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.

 Englishman       Englishmen        the English
 Frenchwoman      Frenchwomen       the French
 Dutchman or      Dutch people      the Dutch
     Dutchwoman

 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)

 Chinese          Chinese           the Chinese
                    (or Chinese people)

 Blackfoot        Blackfoot
 Ojibwa           Ojibwa
 Iroquois         Iroquois
 Blood            Blood
 Mi'kmaq          Mi'kmaq

 Inuk             Inuit