13 Examples of Irregular Plurals
  • 2-minute read
  • 24th December 2022

13 Examples of Irregular Plurals

English is notorious for having many exceptions to its grammar rules. Changing nouns to their plural forms is an example of this, due to the hundreds of irregular nouns in the language. This post will cover the different types of irregular nouns, show their plural forms, and give even more exceptions along the way.

1.   Nouns Ending in -f and -fe → -ves

Singular → Plural

Elf → Elves

Calf → Calves

Wolf → Wolves

Half → Halves

Loaf → Loaves

Knife → Knives

Dwarf → Dwarves

Scarf → Scarves

Self → Selves

Thief → Thieves

Wife → Wives

Exception: Most words ending in -ff, -ief, -oof, and -eef follow standard plural rules and add -s.

Singular → Plural

Belief → Beliefs

Relief → Reliefs

Gulf → Gulfs

Cliff → Cliffs

Beef → Beefs

Reef → Reefs

Hoof → Hoofs or Hooves (although hooves is more common)

2.   Nouns Ending in -o → -oes

Singular → Plural

Potato → Potatoes

Volcano → Volcanoes

Tomato → Tomatoes

Echo → Echoes

Hero → Heroes

Veto → Vetoes


●  Words ending in -io (just add an -s)

●  Words ending in vowel + consonant + o (just add an -s)

●  Some words adopted from other languages


Singular → Plural

Radio → Radios

Audio → Audios

Amnio → Amnios

Scenario → Scenarios

Photo → Photos

Amino → Aminos

Concerto → Concertos or Concerti

3.   Nouns Ending in -y → -ies

Words ending in -y are irregular, and there are also exceptions.

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Singular → Plural

Baby → Babies

City → Cities

Family → Families

Fry → Fries

Exception: If the last two letters of the noun are a vowel + y, then it does not use -ies.

Singular → Plural

Day → Days

Joy → Joys

Ray → Rays

Key → Keys

Bay → Bays

Boy → Boys

4.   Nouns That Change Vowels

Singular → Plural

Foot → Feet

Tooth → Teeth

Goose → Geese

Man → Men

Woman → Women

5.   Nouns That Use -en

Singular → Plural

Child → Children

Ox → Oxen

6.   Nouns That Use Totally Different Words

Singular → Plural

Person → People

Mouse → Mice

Louse → Lice

7.   Animals That are the Same for Singular and Plural

Singular → Plural

Fish → Fish or Fishes (fishes is used when referring to a group of fish of different species)

Deer → Deer

Sheep → Sheep

Moose → Moose

Trout → Trout

Bison → Bison

Cod → Cod

Salmon → Salmon

We use collective nouns when we need to talk about a group of these animals. For example:

A school of fish

A herd of moose

A flock/herd of sheep

A hover of trout

A lap of cod

A run of salmon

Latin and Greek Words

8.   Nouns Ending in -us → -i

Singular → Plural

Focus → Foci or Focuses

Fungus → Fungi

Cactus → Cacti

Nucleus → Nuclei

Radius → Radii or Radiuses

Terminus → Termini or Terminuses

Thesaurus → Thesauri or Thesauruses

Alumnus → Alumni

Some exceptions:

Bonus → Bonuses

Virus → Viruses

Chorus → Choruses

Circus → Circuses

Status → Statuses

9.   Nouns ending in -is → -es

Singular → Plural

Axis → Axes

Crisis → Crises

Thesis → Theses

Analysis → Analyses

Synthesis → Syntheses

10.    Nouns Ending in -um and -on → -a

Singular → Plural

Phenomenon → Phenomena

Criterion → Criteria

Bacterium → Bacteria

Datum → Data (data is often used as a singular and plural noun)

Memorandum → Memoranda

11.    Nouns Ending in -ix and -ex → -ces and -xes, respectively

Singular → Plural

Index → Indices or Indexes

Appendix → Appendices (or appendixes in a medical context)

Vortex → Vortices or Vortexes

12.    Nouns Ending in -ma (Add -ta Suffix)

Singular → Plural

Dogma → Domata

Schema → Schemata

Stigma → Stigmata

Stoma → Stomata

13.    Major Exception: Uncountable Nouns Do Not Have Plural Forms

Uncountable nouns are concepts of things that imply a vague amount. For example:






Some uncountable nouns use quantifiers if you need to specify an amount. For example:

I don’t have a lot of money right now.

I need two cups of flour.

We would like to order two glasses of water.

(Or “We would like two waters.”)

Can you get two gallons/cartons/pints of milk from the store?

I have so much homework to do this evening.


Ultimately, memorizing these irregular nouns and their plural forms is the only way to learn them. However, some patterns (as shown above) can help. If you need help with grammar rules or irregular nouns in your writing, check out our common writing errors guide. Or if you’d like help from an expert, we’ll happily proofread a sample of your work for free!

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