SINGULER AND PLURAL

Regular Plural Forms

The majority of English count nouns are regular and predictable in the spelling of the plural form. Add -s to the end of the singular form or -es to those singulars that end in a sibilant sound (/s/, /z/, /ts/, /dz/). 
 

-s		-es
boy	boys	horse	horses
bed	beds	edge	edges
book	books	patch	patches
pencil	pencils	prize	prizes
day	days	box	boxes

However, if the singular ends with -y and the -y is not preceded by a vowel (or is not a proper name) the -y changes to -i and the plural is then -es. 
 

-y becomes -ies		-y becomes -ys
spy	spies	osprey	ospreys
poppy	poppies	bay	bays
penny	pennies	Germany	Germanys

Outside of this pattern, however, are several nouns which are irregular in their spelling. Below is a semi-comprehensive list compiled from various sources.

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Irregular Plural Nouns - List One

Some nouns that end in -f or -fe are changed to -ves in the plural: 
 

-f or -fe becomes -ves
calf	calves
elf	elves
half	halves
hoof	hooves
knife	knives
leaf	leaves
life	lives
loaf	loaves
scarf	scarfs/scarves
self	selves
sheaf	sheaves
shelf	shelves
thief	thieves
wife	wives
wolf	wolves

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Irregular Plural Nouns - List Two

Some nouns change the vowel sound in becoming plural: 
 

singular	plural
fireman	firemen
foot	feet
goose	geese
louse	lice
man	men
mouse	mice
tooth	teeth
woman	women

Some Old English plurals are still in use: 
 

singular	plural
child	children
ox	oxen

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Irregular Plural Nouns - List Three

Some nouns ending in -o take -s as the plural, while others take -es. 
 

-o becomes -os		-o becomes -oes
auto	autos	echo	echoes
kangaroo	kangaroos	embargo	embargoes
kilo	kilos	hero	heroes
memo	memos	potato	potatoes
photo	photos	tomato	tomatoes
piano	pianos	torpedo	torpedoes
pimento	pimentos	veto	vetoes
pro	pros
solo	solos
soprano	sopranos
studio	studios
tattoo	tattoos
video	videos
zoo	zoos

Some nouns ending in -o take either -s or -es: 
 

singular	plural
buffalo	buffalos/buffaloes
cargo	cargos/cargoes
halo	halos/haloes
mosquito	mosquitos/mosquitoes
motto	mottos/mottoes
no	nos/noes
tornado	tornados/tornadoes
volcano	volcanos/volcanoes
zero	zeros/zeroes

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Irregular Plural Nouns - List Four

Some nouns do not change at all: 
 

singular	plural
cod*	cod*
deer	deer
fish*	fish*
offspring	offspring
perch*	perch*
sheep	sheep
trout*	trout*

*Notice that these are names of fish. Many (but not all!) fish have irregular plural forms. Salmon, pike, halibut and tuna are further examples, but one shark becomes twosharks.

These include nouns that are traditionally plural, but are also used for singular forms: 
 

singular	plural
barracks	barracks
crossroads	crossroads
dice/die	dice
gallows	gallows
headquarters	headquarters
means	means
series	series
species	species

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Irregular Plural Nouns - List Five

Other nouns retain foreign plurals. Note that some of these have adapted a regular English plural form as well. 
 

singular	foreign plural	English plural in use
alga	algae
amoeba	amoebae	amoebas
antenna	antennae	antennas
formula	formulae	formulas
larva	larvae
nebula	nebulae	nebulas
vertebra	vertebrae

Nouns ending in -us with plural -a (only in technical use): 
 

singular	plural
corpus	corpora
genus	genera

Nouns ending in -us with plural -i: 
 

singular	foreign plural	English plural in use
alumnus	alumni
bacillus	bacilli
cactus	cacti	cactuses
focus	foci
fungus	fungi	funguses
nucleus	nuclei
octopus	octopi	octopuses
radius	radii
stimulus	stimuli
syllabus	syllabi	syllabuses
terminus	termini

Nouns ending in -um with plural -a: 
 

singular	Foreign plural	English plural in use
addendum	addenda
bacterium	bacteria
curriculum	curricula	curriculums
datum	data
erratum	errata
medium	media
memorandum	memoranda	memorandums
ovum	ova
stratum	strata
symposium	symposia	symposiums

Nouns ending in -ex, -ix becoming plural -ices: 
 

singular	Foreign plural	English plural in use
apex	apices	apexes
appendix	appendices	appendixes
cervix	cervices	cervixes
index	indices	indexes
matrix	matrices	matrixes
vortex	vortices

Nouns ending in -is becoming -es in plural: 
 

singular	plural
analysis	analyses
axis	axes
basis	bases
crisis	crises
diagnosis	diagnoses
emphasis	emphases
hypothesis	hypotheses
neurosis	neuroses
oasis	oases
parenthesis	parentheses
synopsis	synopses
thesis	theses

Nouns ending in -on becoming -a: 
 

singular	plural
criterion	criteria
phenomenon	phenomena
automaton	automata

Other irregular plurals, retained from different languages: 
 

	singular	plural
Italian	libretto	libretti
	tempo	tempi
	virtuoso	virtuosi
Hebrew	cherub	cherubim
	seraph	seraphim
Greek	schema	schemata

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