This document discusses irregular plurals of nouns in English. It provides examples of several types of irregular plural formations, including nouns that change their final letter before adding -s, change vowels within the word, or have the same form in singular and plural. Common irregular plurals include knives, geese, children, and others that do not follow the regular rule of adding -s.

1. Irregular Plurals of Nouns
Introduction
Although most nouns have plurals formed according to regular rules (see Regular Plurals of
Nouns), some nouns have unusual, or irregular plurals. This page will introduce the most
common ones, so that you can learn them.
Types of irregular plural
There are many types of irregular plural, but these are the most common:
Noun Forming the
Example
type plural
Change f to v knife knives
Ends with
then life lives
-fe
Add -s wife wives
Change f to v half halves
Ends with
then wolf wolves
-f
Add -es loaf loaves
potato potatoes
Ends with
Add -es tomato tomatoes
-o
volcano volcanoes
cactus cacti
ends with
Change -us to -i nucleus nuclei
-us
focus foci
analysis analyses
ends with
Change -is to -es crisis crises
-is
thesis theses
phenomenon phenom
ends with
Change -on to -a ena
-on
criterion criteria
ALL KINDS Change the vowel man men
or foot feet
Change the word child children
or person people
Add a different tooth teeth

2. Noun Forming the
Example
type plural
ending mouse mice
sheep
Unchangin Singular and plural
deer
g are the same
fish (sometimes)
Singular - Plural
Nouns That Have Irregular Plural Forms
When finished, try the Nouns That have Irregular Plural
Forms Quiz
There are some nouns that form the plurals differently.
Some nouns change their vowels in the middle of the
singular form when forming the plural
one goose two geese

3. • foot - feet
• louse - lice
• man - men
• mouse - mice
• tooth - teeth
•&

4. • woman - women
Compounds of words man and woman form plurals the
same way:
• mailman - mailmen
Words that contain the syllable "man" such as in the word
human form the plural by adding the letter s as with most
plurals.
Several nouns form the plural by adding the letters en:
• child - children
• ox - oxen
Some words with descriptive adjectives and hyphens
form the plural by adding the correct affix to the noun
portion of the word.
• father-in-law - fathers-in law
• mother-in-law - mothers-in-law
• brother-in-law - brothers-in-law
• sister-in-law - sisters-in-law
• attorney-general - attorneys-general
• secretary-general - secretaries general
There are a number of animals that have the same
singular and plural form:

5. • bison - bison
• deer - deer
• moose - moose
• sheep - sheep
• swine - swine

6. There are also some animal names that form the plural
the same as the singular or use the s or es form:
• antelope - antelope or antelopes
• cod - cod or cods
• elk - elk or elks
• fish - fish or fishes
• flounder - flounder or flounders
• grouse - grouse or grouses
• herring - herring or herrings
• quail - quail or quails
• reindeer - reindeer or reindeers
• salmon - salmon or salmons
• shrimp - shrimp or shrimps
• trout - trout or trouts
Irregular Plural Nouns
While most nouns are easily made plural with a few simple changes, such as adding an “s” or “es” to the end of the
word, there is one group of nouns that doesn’t seem to follow the rules. They’re called irregular nouns and you
guessed it…they don’t become plural the “regular” way.
No worries, though. Here’s all the information you need to recognize and form irregular plural nouns.
What is an Irregular Plural Noun?
An irregular plural noun is an irregular noun in the plural form. An irregular noun is a noun that becomes plural by
changing it’s spelling in other ways than adding an “s” or “es” to the end of the word. This change can happen in a
variety of ways. Below you’ll find examples and guidelines to help you.

7. Examples of Irregular Plural Nouns
Some irregular nouns take on the plural form by first changing the last letter of the word before adding “s.” Words
that end in “f” are a good example of this case. To make such a word plural, you change the “f” to “ve” and add an
“s.”
Plural nouns that end in ves:
• More than one elf = elves
• More than one calf = calves
• More than one knife = knives
• More than one loaf = loaves
• More than one shelf = shelves
• More than one wolf = wolves
• More than one loaf = loaves
Irregular nouns made plural by changing vowels, changing the word, or adding a different ending:
• More than one man = men
• More than one person = people
• More than one mouse = mice
• More than one child = children
• More than one foot = feet
• More than one goose = geese
• More than one tooth = teeth
• More than one louse = lice
• More than one cactus = cacti
• More than one appendix = appendices
• More than one ox =oxen
Some irregular plural nouns have the same spelling as their singular form such as scissors, pants, bison, deer, and
sheep.And then some animal nouns become plural by keeping the same spelling as the singular form or by adding
an s or es.
• More than one cod = cod or cods
• More than one shrimp = shrimp or shrimps
• More than one fish = fish or fishes
• More than one quail = quail or quails
Like most things, learning the rules for irregular plural nouns takes practice. Once you put these guidelines to work
for you, you’ll find it much easier than you thought.
IRREGULAR PLURALS LIST
Study these groups of words to learn how they change to plural.
Each group of words has similar changes.
US -> I

8. SINGULAR PLURAL
alumnus alumni
cactus cacti
focus foci/focuses
fungus fungi/funguses
nucleus nuclei
radius radii
stimulus stimuli
IS -> ES
SINGULAR PLURAL
axis axes
analysis analyses
basis bases
crisis crises
diagnosis diagnoses
ellipsis ellipses
hypothesis hypotheses
oasis oases
paralysis paralyses
parenthesis parentheses
synthesis syntheses
synopsis synopses
thesis theses
IX -> ICES
SINGULAR PLURAL
appendix appendices
index indeces/indexes
matrix matrices/matrixes
EAU -> EAUX
SINGULAR PLURAL
beau beaux
bureau bureaus/bureaux
tableau tableaux/tableaus
*** -> EN
SINGULAR PLURAL
child children
man men
ox oxen
woman women
*** -> A
SINGULAR PLURAL
bacterium bacteria

9. corpus corpora
criterion criteria
curriculum curricula
datum data
genus genera
medium media
memorandum memoranda
phenomenon phenomena
stratum strata
NO CHANGE
SINGULAR PLURAL
deer deer
fish fish
means means
offspring offspring
series series
sheep sheep
species species
OO -> EE
SINGULAR PLURAL
foot feet
goose geese
tooth teeth
A -> AE
SINGULAR PLURAL
antenna antennae/antennas
formula formulae/formulas
nebula nebulae
vertebra vertebrae
vita vitae
OUSE -> ICE
SINGULAR PLURAL
louse lice
mouse mice