Communication 101

What Are Irregular Plural Nouns?

June 8, 2022
7 Min Read

The large majority of nouns in the English language can be made plural simply by adding “s” or “es” at the end of the word. You turn book into books and rake into rakes. However, there are a number of plural nouns that don’t adhere to this standard. 

Many irregular plural nouns follow a pattern, and some do not, which can make things confusing. You’re likely familiar with many of the hundreds of irregular plural nouns (e.g., men, leaves, feet, etc.). For nouns that don’t follow a pattern, the only way to learn them is to memorize them through speaking or reading. 

Below, Poised explains irregular plural nouns in more detail.

What Is an Irregular Plural Noun?

When a singular noun such as mouse becomes mice in its plural form, that’s how you know you’re dealing with an irregular plural noun in the English language. An irregular plural noun is any plural noun that doesn’t have “s” or “es” at the end of the word like regular plural nouns do.

As stated above, most nouns change from singular to plural by simply adding -s or an -es at the end of the noun. However, there are exceptions to this rule, which can certainly create confusion for someone learning English grammar rules. Unfortunately, irregular plural nouns also have a wide range of different endings when transitioning to their plural form. 

Read on to learn more about common irregular plural nouns and how to use them for effective communication.

What Are the Most Common Irregular Nouns?

Many common irregular plural nouns take on a different singular form. These are important to know, especially for people learning English as a second language. In many cases, there is no rhyme or reason. Instead, it’s a matter of memorization, practice, and repetition to learn the variations of English nouns, parts of speech, and English grammar rules in general.

Let’s discuss some of the most common irregular plural nouns to ensure you know the difference.

Nouns That End in “O”

There are many nouns that end in “o” in their singular form. When they transition to plural, many take on the form of “oes,” such as tomato and tomatoes, potato and potatoes, and flamingo and flamingoes. Unchanging nouns with “o” would be banjo and banjos, or studio and studios

To make matters more confusing, some irregular plural nouns can be spelled with either “os” or “oes.” For instance, banjoes and flamingos are technically correct spellings. 

Here are some other examples of nouns ending with “o” and their plural forms:

  • Buffalo (buffaloes)
  • Cargo (cargos or cargoes)
  • Domino (dominoes)
  • Echo (echoes)
  • Embargo (embargoes)
  • Fresco (frescos or frescoes)
  • Hero (heroes)
  • Torpedo (torpedoes)
  • Zero (zeros)

There’s no hard-and-fast rule for knowing when to spell some irregular plurals with “os” or “oes.” Notice that hero and zero are virtually indistinguishable in form, yet heroes and zeros are the correct plural spellings. These are instances when memorizing through speaking or reading is necessary. 

Nouns That End in “F” or “Fe” 

Most nouns that end in “f” or “fe” change to “ves” in plural form. In other words, for a noun ending in -f, you will change the “f” to a “v” and add “es.” Likewise, for a noun ending in -fe: make the “f” a “v” and add “s.” Both types of irregular plural nouns will end with “ves.” Grammarians initiated this spelling pattern because it’s difficult to pronounce “f” and “s” together; doing so results in a v sound in English. 

Take, for instance, the singular nouns “leaf” and “knife.” The irregular plural nouns become “leaves” and “knives,” respectively.

Other example words that change to “ves” in the plural form are:

  • Life (lives)
  • Loaf (loaves)
  • Wolf (wolves)
  • Wife (wives)

There are exceptions to this rule. Some nouns ending in “f” will take only an “s” at the end. For example:

  • Belief (beliefs)
  • Chief (chiefs)
  • Dwarf (dwarfs)
  • Roof (roofs)
  • Safe (safes)

Another exception is that some nouns can be spelled either way in their plural forms. You can make the “f” a “v” and add “es” or simply add an “s.” A few examples include “beef” (beeves or beefs), “hoof” (hooves or hoofs), and “scarf” (scarves or scarfs). 

Nouns That End in “Us”

Many English words that we use in daily conversation (particularly in mathematical and scientific settings) are borrowed from Latin or Greek. Some of these retain their Latin or Greek plural forms, and some have anglicized plurals that have become common. 

Several singular nouns end in “us,” such as octopus, syllabus, and hippopotamus. When changed to their plural form, the former two become octopi and syllabi. Hippopotami is technically the correct Latin plural form and still regularly shows up in scientific writing.

Many words that come into English have shed their Latin plurals (changing “us” to “i”) and taken the -s or -es form. In this case, hippopotamuses is more appropriate. 

Here are some other examples of nouns ending with “us” and their correct plural forms:

  • Alumnus (alumni or alumna)
  • Cactus(cacti)
  • Focus (foci or focuses)
  • Fungus (fungi)
  • Nucleus (nuclei)
  • Radius(radii or radiuses)
  • Testis (Testes)
  • Oasis (Oases)
  • Octopus (Octopodes)
  • Memorandum (Memoranda)
  • Larva (Larvae)
  • Louse (Lice)
  • Addendum (Addenda)

As you can see, many -us nouns can be spelled with the -i or -es form. It typically sounds more natural to use the anglicized “es” form in informal communication. For instance: focuses instead of foci. If you often use the word radius, it likely means you work in mathematics. Therefore, radii would sound completely normal to you!

Nouns That Use Different Vowels When Plural

Many common nouns change vowels in their plural forms. This includes changing “oo” to “ee” or “an” to “en.” You’ll notice this in words like tooth and teeth, foot and feet, man and men, woman and women, mouse and mice, and goose and geese. These are other instances when memorization through speaking or writing is the only way to learn the correct spelling because there isn’t a standard pattern or rule to follow. 

Nouns That Use Different Consonants When Plural

If you thought changing vowels was a big deal, did you know that some irregular plural nouns change even more substantially? Some even change their consonants in the middle! For various historical reasons, certain nouns completely shift in spelling to achieve a plural form.

Take a look at the following examples:

  • Sphinx (sphinges)
  • Nieces and nephews (niblings)
  • Plankter (plankton)
  • Forum (fora or forums)
  • Index (indices or indexes)
  • Person (people)
  • Vertex (vertices)
  • Ovum (Ova)

Nouns That Are the Same When Singular or Plural

Some types of nouns are the same when singular or plural.

These are singular nouns that have no change in their plural forms, such as aircraft, shrimp, elk, moose, and trout. These nouns stay the same, and the context of the sentence dictates whether they are singular or plural. These nouns can be common mistakes that elude even the best of communicators.

Here are some other examples to consider:

  • Bison
  • Bread
  • Caribou
  • Deer
  • Jeans
  • Meat
  • Offspring
  • Pants
  • Pliers
  • Reindeer
  • Salmon
  • Salt
  • Swine
  • Trousers

What Are Some Examples of Irregular Plurals in Sentences?

So, you’re starting to get the gist of what makes a plural noun irregular. Let’s take a look at some example sentences that contain irregular plural nouns:

  1. I made a delicious dish for the family, and everyone cleaned the dishes afterward.
  2. All the dominoes fell after she pushed the first one.
  3. The government ordered embargoes until they could regain control of the ports.
  4. The password included three zeros.
  5. The grocery store had only two loaves of bread left.
  6. The pack of wolves went hunting in new territory.
  7. A man who doesn't hold true to his beliefs cannot be trusted.
  8. The roofs on all the homes in the neighborhood were damaged by hail.
  9. They couldn't solve the problem without first calculating all the radii.
  10. The dentist recommended extracting the decayed tooth for the sake of all the other teeth.
  11. The geese stuck together as they terrorized the golfers.
  12. You could see a handful of deer through the brush.
  13. He took the pliers out of his toolbox.
  14. The workers put so much bread on the shelves.
  15. The University is known for its distinguished alumni.

Learn To Communicate Effectively

If you hope to become an impactful communicator, it's essential to understand how irregular plural nouns work. Most nouns in the English language simply require an "s" or "es" to convert into plural form. And some irregular plural nouns follow formulas, making them quite easy to learn.

Most irregular plurals require you to learn their spellings through memorization. Practicing speaking the English language and reading a variety of genres are the most practical ways to get a grasp of irregular plurals. As you speak, listen to others, and read, take note of the words and phrases you come across so that you can gradually learn how to make each noun plural.

How Poised Can Help

Another way to improve as a communicator is to use an AI-powered coach like Poised. Our software provides real-time pointers on the language you use in meetings and analyzes your performance over the long term. That way, you can become a better communicator with each video meeting and track your progress over time.


100 Irregular Plural Nouns in English | ThoughtCo.

Plurality in English and Other Languages: Does It Add Up? | OpenEdition Journals

Plurals Of English Nouns |

What is a Noun? || Oregon State Guide to Grammar | College of Liberal Arts

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