The following are the Rules of formation of Plural Number —


#1. In most cases by adding ‘s’ to the Singular Number. As –
Singular
Plural
Singular
Plural
Boy
Girl
Pen
Table
Boys
Girls
Pens
Tables
Question
Problem
Book
House
Questions
Problems
Books
Houses

#2. By adding ‘es’ to the Singular Number in words ending in ‘s’, sh’, ch’, or ‘x’. As –
Singular
Plural
Singular
Plural
Class
Kiss
Lass
Dish
Brush
Classes
Kisses
Lasses
Dishes
Brushes
Match
Watch
Branch
Tax
Box
Matches
Watches
Branches
Taxes
Boxes

#3. In word ending in ‘o’ generally ‘es’ is added. As –
Singular
Plural
Singular
Plural
Buffalo
Potato
Negro
Hero
Echo
Zero
Buffaloes
Potatoes
Negroes
Heroes
Echoes
Zeroes
Mango
Cargo
Volcano
Motto
Mosquito
Mangoes
Cargoes
Volcanoes
Mottoes
Mosquitoes

Exceptions:–
Singular
Plural

Canto
Piano
Dynamo
Solo
Memento
Photo
Ratio
Quarto
Cantos
Pianos
Dynamos
Solos
Mementos
Pbotos
Ratios
Quartos

#4. But in words ending in ‘oo’, ‘io’, ‘eo’ or ‘yo’ only ‘s’ is added. As –
Singular
Plural
Singular
Plural
Bamboo
Cockoo
Curio
Cameo
Bamboos
Cuckoos
Curios
Cameos
Portfolio
Embryo
Ratio
Stereo
Portfolios
Embryos
Ratios
Stereos
#5. When a word ends in ‘y’, and before ‘y’ there is a consonant, ‘y’ is replaced by ‘ies’. As –
Singular
Plural
Singular
Plural
Baby
Army
Lady
Story
Babies
Armies
Ladies
Stories
City
Pony
Duty
Fly
Cities
Ponies
Duties
Flies

But if there is a Vowel before ‘y’, (as ‘ay’, ‘ey’, ‘oy’) only ‘s’ is added. As –
Singular
Plural
Singular
Plural
Day
Play
Key
Days
Plays
Keys
Boy
Toy
Monkey
Boys
Toys
Monkeys

#6. In words ending in ‘f’ or ‘fe’ in the Singular, ‘f’ or ‘fe’ are replaced by ‘ves’. As –
Singular
Plural
Singular
Plural
Knife
Life
Wife
Calf
Elf
Half
Loaf
Knives
Lives
Wives
Calves
Elves
Halves
Loaves
Leaf
Myself
Sheaf
Shelf
Thief
Wolf

Leaves
Ourselves
Sheaves
Shelves
Thieves
Wolves


Exceptions:–
Singular
Plural
Singular
Plural
Belief
Chief
Cliff
Dwarf
Grief
Gulf
Hoof
Brief
Beliefs
Chiefs
Cliffs
Dwarfs
Griefs
Gulfs
Hoofs
Briefs
Proof
Roof
Safe
Scarf
Strife
Turf
Wharf
Serf
Proofs
Roofs
Safes
Scarfs
Strifes
Turfs
Wharfs
Serfs

#7. In the following eight Nouns, changes are made in the Vowels used within them. As –
Singular
Plural
Singular
Plural
Man
Woman
Foot
Tooth
Men
Women
Feet
Teeth
Mouse
Louse
Goose
Dormouse
Mice
Lice
Geese
Dormice

#8. In the following four Nouns, ‘en’ or ‘ne’ are added. They are –
Singular
Plural
Singular
Plural
Child
Ox
Children
Oxen
Cow
Brother
Kine (but also cows)
Brethren (but also brothers)

#9. Some Nouns remain the same both in the Singular and Plural forms. As –
Public, Police, Innings, Gross, Yoke, Brace, Sheep, Deer, Fish, Swine, Hair, Dozen, Score, Hundred, Thousand, Pound, Kilogram, Series, Species, Means.

#10. The Plurals of Compound Nouns are formed by adding ‘s’ to the Principle word in the compound form. As –
Singular
Plural
Singular
Plural
Commander-in-chief
Son-in-law
Daughter-in-law
Brother-in-law
Father-in-law
Commanders-in-chief
Sons-in-law
Daughters-in-law
Brothers-in-law
Fathers-in-law
Maid-servant
Passer-by
Looker-on
Man-of-war
Step-son
Maid-servants
Passers-by
Lookers-on
Men-of-war
Steps-sons
#11. For forming the Plurals of Letters, Alphabet, Figures, Abbreviations and Symbols, Apostrophe -'s ('s) is added. As –
  • a's, b's, r's, 5's, 3's
  • M.A.'s, M.L.A.'s, B.A.'s
  • Dot your i's and cut your t's.
  • Your b's are not clear.
  • His R's are peculiar.
  • Your 5's look like 3's.
Note:– The Plural of ‘p’ (page) is ‘pp’ and of ‘l’ (line) is ‘ll’.

#12. Sometimes Surnames can be used in the Plural Number. As –
  • Miss Smith – the Miss Smiths or the Misses Smith.
  • Mr. Ray – the Rays.
#13. We give below the Plurals of some popular foreign words (Greek, Latin, etc.)
Singular
Plural
Singular
Plural
Agendum
Alumnus
Appendix
Axis
Datum
Dictum
Erratum
Formula
Fungus
Genius
Index
Agenda
Alumni
Appendices
Axes
Data
Dicta
Errata
Formulae/Formulas
Fungi
Genii
Indices
Medium
Memorandum
Radius
Analysis
Basis
Crisis
Criterion
Oasis
Phenomenon
Thesis
Cherub
Seraph
Media
Memoranda
Radii
Analyses
Bases
Crises
Criteria
Oases
Phenomena
Theses
Cherubim
Seraphim
Note:– In English ‘Agenda’ is used as a Singular Number only.