Forming plural nouns in English

I. Regular plurals

The regular plural is formed by adding the suffix -s to the singular: e.g. cat — cats, table — tables.

II. Irregular plurals

1. Nouns in -ss, -sh, -ch, -x
Nouns ending in -ss, -sh, -ch, -x form their plural by adding -es:
e.g. glass — glasses, dish — dishes, peach — peaches, box — boxes.

2. Nouns in -o
Nouns ending in -o form their plural by adding -es if they are used frequently they have been introduced into English early:
e.g. tomato — tomatoes, hero — heroes
They add -s only if they are of foreign origin or abbreviated words:
e.g. bamboo — bamboos, kilo — kilos.
A number of nouns ending in -o can take both -s and -es:
e.g. tornado — tornados or tornadoes, motto — mottos or mottoes.

3. Nouns in -y
Nouns ending in -y preceded by a consonant form their plural by changing -y into -i and adding -es:
e.g. fly — flies, country — countries.
Nouns ending in -y preceded by a vowel form their plural by adding -s only:
e.g. boy — boys, journey —journeys.

4. Nouns in -f or -fe
The following nouns ending in -f or -fe form their plural by changing the -f into -adding -es:
e.g. calf — calves, wife — wives. These are the following nouns:
calf, life, shelf, half, loaf, thief, knife, self, wife, leaf, sheaf, wolf
Some nouns ending in -f can either take -s or change the -f into -v- and add -es
e.g. dwarf— dwarfs or dwarves scarf — scarfs or scarves.
Other nouns ending in -f or -fe form their plural in the regular way:
e.g. handkerchief— handkerchiefs, fife —fifes.

5. Mutation
The following nouns form their plural by a vowel change:
foot — feet, louse — lice, man — men, goose — geese, mouse — mice, woman — women, tooth — teeth

6. The -en plural
The following nouns form their plural by adding -en to the singular:
brother — brethren (i.e. 'fellow members of a religious society') child — children ox — oxen.

7. Foreign nouns
Words of foreign origin often form their plural according to the rules of a specific language:
a) Latin: stimulus — stimuli, larva — larvae, curriculum — curricula, codex — codices.
b) Greek: basis — bases, criterion — criteria.
c) French: bureau - beueaux
d) Italian: tempo - tempi
However, foreign plurals sometimes occur along with regular plurals:
e.g. index — indices, indexes , antenna — antennae, antennas, which indicate two different meanings or only the regular plural is used:
e.g. album — albums, metropolis — metropolises.

8. Zero plural
Some nouns do not have a separate plural form:
a) the names of certain animals, birds, and fish: e.g. sheep, grouse, trout
A sheep is a grass-eating animal.
Sheep are kept for their flesh as food and for their wool.
b) nouns denoting people of one nationality and ending in -ese or -ss:
e.g. Vietnamese, Swiss
Yesterday I met a Vietnamese.
The Vietnamese are natives of Vietnam.
c) craft (meaning 'boat') and aircraft:
e.g. I have a handy and useful little craft.
You can see all kinds of craft in the harbour.
d) definite numbers and measurements:
e.g. two hundred years, two score eggs
but indefinite numbers and measurements take the plural form:
e.g. hundreds of years, kilos of oranges.
Note that the form five kilos of oranges is also used.
e) offspring occurs with a singular verb if it refers to one human or animal and it is followed by a plural verb if it refers to more than one:
e.g. Their offspring is extremely intelligent. Their offspring are all slightly stupid.

9. Compounds
a) The final element of compounds is usually pluralized:
e.g. breakdown — breakdowns, bookcase — bookcases.
b) In compounds whose first element is man or woman both elements are made plural:
e.g. gentleman farmer — gentlemen farmers woman doctor — women doctors.
c) Compounds consisting of countable nouns and prepositions or prepositional phrases take the plural inflection on nouns:
e.g. passer-by — passers-by, mother-in-law — mothers-in-law. d) Compounds formed by verbs or adjectives and prepositions take the plural at the end:
eg.take-off — take-offs, grown-up — grown-ups.
e) Compounds (typical of legal English) consisting of countable nouns and lake the plural inflexion on nouns:
e.g. attorney general — attorneys general, notary public — notaries public
but it is also possible to have alternative forms:
e.g. court-martials, postmaster-generals
f) Nouns ending in -ful become plural in two ways:
e.g. spoonful — spoonfuls, handful — handfuls or handsful.
g) Compounds whose last element is a mass noun do not form the plural:
e.g. sunshine, homework.

10) Proper nouns
Only surnames can be used in the plural and then they denote a family. Such plurals are formed by adding -s:
e.g. Mr. and Mrs. Brown = the Browns
Mr. and Mrs. Crosby = the Crosbys
except for names ending in a sibilant as in Mr. and Mrs. James = the Jameses, where -es in added.

Rules in forming the plural of nouns. The spelling rules of plural nouns.

General rules

Regular spelling   Singular Plural
'-s' in most cases   cat cats
tub tubs
dog dogs
house houses
'-es' when a noun ends with: -o potato potatoes
tomato tomatoes
-ss class classes
-x box boxes
-ch watch watches
-sh bush bushes
words of foreign origin take '-s'
-o dynamo dynamos
kilo kilos
kimono kimonos
photo photos
piano pianos
soprano sopranos
consonant + -y turns into ies country countries
baby babies
fly flies
lady ladies
cry cries
vowel + y takes '-s' -ay day days
-ey key keys
-oy boy boys
-uy guy guys
proper nouns   Fry the Frys
  Kennedy the Kennedys
nouns ending with -f / -fe -ves loaf loaves
knife knives
life lives
calf calves
leaf leaves
shelf shelves
thief thieves
wife wives
wolf wolves
half halves
wharf wharves
EXCEPTIONS   chief chiefs
cliff cliffs
handkerchief handkerchiefs
roof roofs
some nouns have both forms -s or -ves hoof hoofs / hooves
scarf scarfs / scarves
dwarf dwarfs / dwarves
nouns which change vowels   foot feet
  louse lice
  mouse mice
  woman women
  goose geese
  man men
  tooth teeth
  child children
  ox oxen