100 Irregular Plural Nouns in English

Examples of Irregular Plural Nouns in English
ThoughtCo./Melissa Ling

Most English nouns form their plural by adding either -s (books, bands, bells) or -es (boxes, bunches, batches). These plural forms are said to follow a regular pattern.

Irregular Plural Nouns

"The Penguin Writer's Manual"

"There are no easy rules, unfortunately, for irregular plurals in English. They simply have to be learnt and remembered."

Not all nouns conform to the standard pattern. In fact, some of the most common English nouns have irregular plural forms, such as woman/women and child/children. In addition, several nouns have alternative plurals, one regular and the other irregular.

In regard to these alternative forms, there are no strict rules to guide our use of them.

"The Cambridge Encyclopedia of the English Language"

"People have to learn which form to use as they meet the words for the first time, and must become aware of variations in usage. When there is a choice, the classical [irregular] plural is usually the more technical, learned, or formal, as in the case of formulas vs. formulae or curriculums vs. curricula. Sometimes, alternative plurals have even developed different senses, as in the cases of (spirit) mediums vs. (mass) media, or appendixes (in bodies or books) vs. appendices (only in books)."

As you'll see in the list that follows, many words with irregular plurals are loanwords that have kept their foreign plural forms (or at least held on to those forms as alternatives to regular English plurals).

100 Irregular Plural Nouns List

In the list below, you'll find singular noun forms in the left column and the corresponding plural forms in the right column. When a noun has more than one plural form, the irregular one appears first, though that doesn't necessarily mean that the irregular form is more widely accepted than the regular form.

addendum addenda or addendums
aircraft aircraft
alumna alumnae
alumnus alumni
analysis analyses
antenna antennae or antennas
antithesis antitheses
apex apices or apexes
appendix appendices or appendixes
axis axes
bacillus bacilli
bacterium bacteria
basis bases
beau beaux or beaus
bison bison
bureau bureaux or bureaus
cactus cacti or cactus or cactuses
château châteaux or châteaus
child children
codex codices
concerto concerti or concertos
corpus corpora
crisis crises
criterion criteria or criterions
curriculum curricula or curriculums
datum data
deer deer or deers
diagnosis diagnoses
die dice or dies
dwarf dwarves or dwarfs
ellipsis ellipses
erratum errata
faux pas faux pas
fez fezzes or fezes
fish fish or fishes
focus foci or focuses
foot feet or foot
formula formulae or formulas
fungus fungi or funguses
genus genera or genuses
goose geese
graffito graffiti
grouse grouse or grouses
half halves
hoof hooves or hoofs
hypothesis hypotheses
index indices or indexes
larva larvae or larvas
libretto libretti or librettos
loaf loaves
locus loci
louse lice
man men
matrix matrices or matrixes
medium media or mediums
memorandum memoranda or memorandums
minutia minutiae
moose moose
mouse mice
nebula nebulae or nebulas
nucleus nuclei or nucleuses
oasis oases
offspring offspring or offsprings
opus opera or opuses
ovum ova
ox oxen or ox
parenthesis parentheses
phenomenon phenomena or phenomenons
phylum phyla
quiz quizzes
radius radii or radiuses
referendum referenda or referendums
salmon salmon or salmons
scarf scarves or scarfs
self selves
series series
sheep sheep
shrimp shrimp or shrimps
species species
stimulus stimuli
stratum strata
swine swine
syllabus syllabi or syllabuses
symposium symposia or symposiums
synopsis synopses
tableau tableaux or tableaus
thesis theses
thief thieves
tooth teeth
trout trout or trouts
tuna tuna or tunas
vertebra vertebrae or vertebras
vertex vertices or vertexes
vita vitae
vortex vortices or vortexes
wharf wharves or wharfs
wife wives
wolf wolves
woman women


  • Crystal, David. "The Cambridge Encyclopedia of the English Language." 3rd Edition, Cambridge University Press, January 24, 2019.
  • Manser, Martin. "Penguin Writers Manual." Penguin Reference Books, Stephen Curtis, Paperback, International Edition, UK ed. edition, Penguin UK, August 24, 2004.