Irregular Plural Nouns

Regular vs. irregular nouns

In English, we tend to like to define things by kind or type. Similar to how regular and irregular verbs are categorized by the use of -ed in the past tense, nouns have their own way to separate between regular and irregular. The difference between regular and irregular nouns is this:

• Regular nouns end in -s / -es in their plural forms.

• Irregular nouns end in something other than -s / -es in their plural forms.

When it comes to nouns, we obviously aren’t speaking about the change a noun goes through in tense, since nouns have no tense. Instead, it’s how a noun changes in its form to mean one thing (or person, place), or more than one thing/person/place (e.g., the change from singular to plural). By and large, the majority of English nouns use the conventional -s or -es to indicate a plural:

• dog ➜ dogs
• cat ➜ cats
• table ➜ tables
• fox ➜ foxes
• tomato ➜ tomatoes

These are regular nouns since they add s/es as a plural. As you can see from the list above, some just add an s, where others add es. When should you use s or es? And what do irregular nouns end in if not s/es? This will be answered, and we’ve also written out a list in this article of each of the irregular plural nouns in English, for your convenience and use.

Regular noun endings

Most nouns will just add n -s. However, we add es to singular nouns that end in –s, –ss, –sh, –ch, –z and sometimes -o; as in:

• dress ➜ dresses
• ash ➜ ashes
• bench ➜ benches
• box ➜ boxes
• tomato ➜ tomatoes
• quiz ➜ quizzes

Notice how some of the nouns above that end in “z” or “s” adds a double “z” or “s” before “es” (this is the correct form for nouns ending in “z” or “s”). With nouns that end in “y” as a singular, we replace the “y” with “ies” as a plural:

• puppy ➜ puppies
• baby ➜ babies

If the letter before the “y” is a vowel and not a consonant, add “s’ (not “ies”; e.g., ray/rays, boy/boys). Most nouns that end in “ff”, “f” or “ef” add “s” as a plural, but some nouns that end in “f” or “fe” add “ves” as a plural. See the difference:

• belief ➜ beliefs
• cliff ➜ cliffs
• chief ➜ chiefs
• roof ➜ roofs
• chef ➜ chefs

Whereas other nouns ending in “f” or “fe” add “ves” as a plural:

• wolf ➜ wolves
• calf ➜ calves
• knife ➜ knives
• wive ➜ wives

Singular nouns that end in “o” usually add “es” as a plural, but not always. Some will just add “s”, others “es”, and (this part gets really whacky) with some nouns, you can use either “s” or “es”. The options are practically endless. Take a look:

• tomato ➜ tomatoes
• potato ➜ potatoes
• volcano ➜ volcanoes (or volcanos)
• mango ➜ mangoes (or mangos)

These nouns that end in “o” just add “s”:

• video ➜ videos
• photo ➜ photos
• halo ➜ halos

Irregular noun patterns

By looking at them, it appears like irregular plurals follow no rules, but if you look closely, you’ll see patterns that makes learning them much easier. Apologies for the repetitiveness, but just like when it comes to learning irregular verb forms, recognizing the patterns amongst their irregular-ness is an extremely effective way to remember them (I encourage it). Let’s get into the nuts and bolts of these ostensibly irregular nouns.

Some nouns add -en, or swap their inner vowels with another pair of vowels:

These nouns add -en:

• child ➜ children
• ox ➜ oxen

These nouns swap their inner vowels:

• woman ➜ women
• man ➜ men
• person ➜ people
• mouse ➜ mice

These swap their inner vowels of double o’s with e’s:

• goose ➜ geese
• tooth ➜ teeth
• foot ➜ feet

Side-note: don’t get confused—just because goose is geese plural, doesn’t mean moose becomes meese!

Nouns that end in -sis usually switch to ses as a plural:

• synopsis ➜ synopses
• crisis ➜ crises
• oasis ➜ oases

Latin nouns that end in -um switch to -a:

• memorandum ➜ memoranda
• curriculum ➜ curricula
• colloquium ➜ colloquia

Latin nouns that end in -ix switch to -ces/-xes:

• matrix ➜ matrices/matrixes

• apex ➜ apices/apexes

• index ➜ indices/indexes

Some nouns don’t change at all from singular to plural:

• sheep ➜ sheep

• deer ➜ deer

• aircraft ➜ aircraft

A mass noun names something we cannot physically count, or things that exist in a form which cannot be counted, either because they are abstract or too numerous to count. Because of this, abstract or mass nouns stay singular in form. Some examples are:

• water

• oil

• sand

• art

A comprehensive list of irregular nouns in English

Singular	Plural
city	cities
baby	babies
pony	ponies
oasis	oases
diagnosis	diagnoses
synthesis	syntheses
thesis	theses
paralysis	paralyses
psychosis	psychoses
synopsis	synopses
analysis	analyses
crisis	crises
hypothesis	hypotheses
prognosis	prognosis
basis	bases
ellipsis	ellipses
parenthesis	parentheses
goose	geese
foot	feet
tooth	teeth
child	children
man	men
woman	women
person	people
ox	oxen
die	dice
louse	lice
mouse	mice
fungus	fungi/fungasses
octopus	octopi/octopuses
syllabus	syllabi/syllabuses
stimulus	stimuli/stimuluses
alumnus	alumni
platypus	platypi/platypuses
locus	loci/locuses
radius	radii/radiuses
focus	foci/focuses
larva	larvae/larvas
genus	genera/genuses
datum	data
bacterium	bacteria
criterion	criteria
medium	media
addendum	addenda/addendums
referendum	referenda/referendums
memorandum	memoranda/memorandums
symposium	symposia/symposiums
colloquium	colloquia/colloquiums
phenomenon	phenomena/phenomenons
spectrum	spectra/spectrums
curriculum	curricula/curriculums
index	indices/indexes
shelf	shelves
elf	elves
knife	knives
life	lives
self	selves
wife	wives
wolf	wolves
calf	calves
half	halves
bison	bison
cactus	cacti/cactuses
scarf	scarves
shrimp	shrimp
moose	moose
deer	deer
sheep	sheep
fish	fish
tomato	tomatoes
potato	potatoes
hero	heroes
echo	echoes
volcano	volcanoes
zero	zeroes
appendix	appendices/appendixes
axis	axes
apex	apices/apexes
matrix	matrices/matrixes
vortex	vortices/vortexes
vertex	vertices/vortexes

Sources

‍

1. Irregular Plurality

‍