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50+ Irregular Plural Nouns in English

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Let’s learn 50 irregular plural nouns – these are nouns that don’t follow the normal rules for forming plurals! Even a lot of native English speakers aren’t sure about how to make the plural forms of these words. When you learn them, you can avoid mistakes and then be confident that your English is correct.

Let’s quickly review how we form regular plural nouns, and then we’ll get to the irregular ones and more complicated cases.

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Regular Plural Nouns:

Add -S

  • wall – walls
  • ski – skis
  • cat – cats

Nouns Ending In -Ch, -Sh, -X, -S Sounds:

Add -ES

  • switch – switches
  • brush – brushes
  • box – boxes
  • address – addresses

Exceptions: stomach/stomachs, matrix / matrices

Nouns Ending In consonant-Y:

End With -IES

  • baby – babies
  • army – armies
  • puppy – puppies

If the noun ends in vowel-y: just add -S

  • day – days
  • key – keys
  • toy – toys
The plural of puppy is puppies (not puppys)

Nouns Ending In -O:

-S Or -ES (Depends On The Word!)

Words that end in a vowel + o: Just add -s

  • zoo – zoos
  • radio – radios
  • video – videos
  • tattoo – tattoos

Musical words: Just add -s

  • solo – solos
  • piano – pianos
  • cello – cellos

Words from Italian/Spanish: Just add -s

  • taco – tacos
  • avocado – avocados
  • tornado – tornados
  • casino – casinos
The plural of taco is tacos

Shortened words: Just add -s

  • photo – photos
  • kilo – kilos
  • auto – autos
  • pro – pros

Always –ES:

  • potato/tomato – potatoes/tomatoes
  • hero – heroes
  • torpedo – torpedoes
  • echo – echoes
The plural of potato is potatoes

Some can be both!

  • ghetto – ghettos / ghettoes
  • mango – mangos / mangoes
  • mosquito – mosquitos / mosquitoes
  • volcano – volcanos / volcanoes

Nouns Ending In -F Sound: Change To -VES

  • knife – knives
  • wife – wives
  • half – halves
  • life – lives
  • self – selves
  • wolf – wolves
  • leaf – leaves

Exceptions: chef/chefs and roof/roofs

The plural of knife is knives

VERY Irregular Nouns

  • man – men
  • woman – women
  • child – children
  • person – people
  • tooth – teeth
  • foot – feet
  • die – dice
  • vertebra – vertebrae
  • antenna – antennas (electrical) and antennae (insects)
  • mouse – mice
  • goose – geese
  • ox – oxen
The plural of die is dice

Nouns with the same singular and plural form

  • one sheep, two sheep
  • one deer, two deer
  • one fish, two fish
  • one series, two series
  • one species, two species
The plural of deer is deer

Latin/Greek Nouns: US –> I

  • alumnus/alumna – alumni
  • cactus – cacti
  • focus – foci
    Some people do say “focuses.” Alternatively, you could say “points of focus” or “focal points” for the plural of “focus”
  • fungus – fungi
  • nucleus – nuclei
  • stimulus – stimuli
  • syllabus – syllabi
The plural of cactus is cacti

Latin/Greek Nouns: IS –> ES

  • analysis – analyses
  • axis – axes
  • basis – bases
  • crisis – crises
  • diagnosis – diagnoses
  • hypothesis – hypotheses
  • oasis – oases

Latin/Greek Nouns: UM/ON –> A

  • bacterium – bacteria
  • criterion – criteria
  • curriculum – curricula
  • datum – data
  • millennium – millennia
  • phenomenon – phenomena

Learn more: 10 types of nouns

Do you think you can remember all those irregular plural nouns? Try using as many as you can in sentences!

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