An English plural – that is, the plural form of a singular noun – is most commonly formed by adding an s to the singular form:
boy boys girl girls table tables
Where a noun ends in a sibilant sound – such as s, sh, x, soft ch – the plural is formed by adding es:
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
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 dwarf / dwarves hoof hoofs / hooves roof roofs / rooves staff staffs / staves turf turfs / turves
Notes:
- dwarf is an interesting case: the common form of the plural was dwarfs – e.g., in Walt Disney's Snow White and the Seven Dwarfs – until J.R.R. Tolkien came along and popularised dwarves. Multiple dwarf stars, however, are dwarfs.
- staff: in the sense of "a body of employees" the plural is always staffs; otherwise both staffs and staves are OK, except in compounds; e.g., flagstaffs
Nouns ending in y, preceded by a consonant, change their ending to ies:
cherry cherries lady ladies
A plural can also be formed from the singular by adding en:
ox oxen
This also turns up in rural English dialects:
eye eyen shoe shoon
The plural is sometimes formed by simply changing the vowel sound of the singular (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
Some nouns have no singular form:
annals billiards cattle clothes measles nuptials thanks tidings vituals
Neither do the names of things having two parts:
scissors trousers tweezers
Some nouns have no plural form.
- abstract nouns
goodness idleness wisdom
- chemical elements
antimony gold oxygen
- arts and sciences (those ending in ics are treated as singular!)
chemistry geometry surgery
biometrics mechanics optics
- non-countable nouns
furniture adolescence
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 pea peas pease penny pennies pence sow sows swine
Notes:
- 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
- pease turns up in pease pudding, but more people know the rhyme than have ever eaten the dish
- 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
Because English includes words from so many ancestral languages, as well as many loanwords from Classical Greek and Latin and from other modern languages, there are many other forms of plurals. Such nouns usually retain their original plurals, at least for some time after they are introduced. In some cases both forms are still vying for attention: e.g., for a librarian, the plural of appendix is appendices (following the original language); for physicians, however, the plural of appendix is appendixes. The "correct" form is the one that sounds the better in context.
- final a becomes ae (strictly æ) – or just adds s
formula formulae / formulas
- final ex becomes ices – or just adds es
vertex vertices
index indices / indexes
- final is becomes es
axis axes
- final on becomes a
phenomenon phenomena
- final um becomes a – or just adds s
addendum addenda
memorandum memoranda / memorandums
- final us becomes i (second declension) or era (third declension) – or just adds es
radius radii
viscus viscera
virus viruses
- some nouns of French origin add x
beau beaux
- nouns of Hebrew origin add im or ot (generally m/f) – or just s
note that ot is pronounced os in Ashkenazi
cherub cherubim / cherubs
seraph seraphim / seraphs
matzoh matzot / matzos
Some words of foreign origin are much better known in the plural, while the singular is hardly ever used:
candelabrum candelabra datum data grafitto grafitti insigne insignia viscus viscera