Only s is added
Crocodile
Monster
Movie
Boat
Coat
Cat
Truck
Bag
Tree
Ending with us, SS ch, sh, x, z, o, es is added
BUS
WISH
Brush
Pitch
Switch
Dish
Glass
Potato
Bench
Box
Buffalo
Changing oo into the ee
Tooth – teeth
Goose – geese
Foot – feet
Changing vowels in the middle
Mouse – mice
Index – indices
Vertex – vertices
By adding en, ren,
Ox – oxen
Woman – women
Child- children
Man – Men
Fireman – firemen
Person –people
By adding e
Alumina – alumnae
Antenna – antennae
Larva – larvae
Nebula – nebulae
Pupa – pupae
Vita- vitae
Alga – algae
F is replaced by, ves
Wolf –wolves
She wolf- she wolves
Knife – knives
Calf – calves
Loaf –loves
Wife – wives
Life – lives
Elf – elves
Half – halves
F is NOT replaced
Belief – beliefs
Chef – chefs
Chief – chiefs
Dwarf – dwarfs
Proof- proofs
Roof – roofs
Safe – safes
Us is replaced by I
Radius-Radii
Fungus – fungi
Locus – loci
Nucleus- nuclei
Stimulus – stimuli
Syllabus – syllabi
Terminus – termini
Focus – foci
Cactus – cacti
Alumnus – alumni
Bacillus – bacilli
If there is a consonant before y, y is replaced by ies
Lady – ladies
City –cities
Spy – spies
Penny – pennies
Fairy – fairies
If there is a vowel before y , only s is added
Ray – rays
Key – keys
Toy – toys
Boy – boys
final’ um’ to’ a’ to
Bacterium – Bacteria
Curriculum – curricula
Datum – Data
Erratum – Errata
Gymnasium – Gymnasia
Medium – media
Memorandum – memoranda
Ovum – ova
On is changed into a
Criterion – criteria
Phenomenon Phenomena
Others words-
Diagnosis – diagnoses
Thesis – Theses
Analysis – analyses
Crisis – crises
He man
Lady in waiting
Lieutenant colonel
Middle class
Post office
Secretary of state
Step sister
Passer by
A looker on
Son in law
Daughter in law
Bill of fare
Chief of staff
Full moon
Remains unchanged (singular & plural forms are same)
Advice
Aircraft
Corn
Deer
Gold
Evidence
Information
Kin
Luck
Fish
Wheat
Luggage
Moose
Legislation
Offspring
Sheep
Silver
Swine
Trousers
Crockery
Footwear
Harm
Nonsense
Perseverance
Italics
Linguistics
News
Phonetics
Physics
Exist only in plural forms (UNCOUNTABLES, MATERIALS,LANGUAGES, ABSTRACTS etc)
Barracks
Cattle
Grief
Congratulations
Deer
Eyeglasses
Headquarters
Mathematics
Means
Oats
Pants
Pliers
Scissors
Series
Shears
Shorts
Species
Tongs
Athletics
Linguistics
Alms
Belongings
Clothes
Police
Vermin
Clothing
Equipment
Footwear