However, certain nouns have irregular plurals which do not behave in this standard way and, even though most irregular plurals follow a pattern, there are always exceptions to watch out for.

Regular Plurals

The general rule for making a noun plural is that if the word ends in s, x, z, ch or sh, add an "es"

Bless = blesses
Box = boxes
Catch = catches
Dish = dishes
Buzz = buzzes

An exception to this rule is if the ch ending is pronounced with a "k" sound you add "s" rather than "es"

stomach = stomachs

If the word ends in a consonant (all letters except a, e, i, o, u) plus "y," then change the "y" to an "i" and add the letters "es"

Baby = babies
Candy = candies

For all other non-irregular nouns, simply add an "s" to the end of the word

Cat = cats
Dog = dogs

Irregular Plurals

Certain words do not follow the above rules for regular plurals. There are some common types of irregular plurals that occur, and some words simply have no plural form at all.

While it is useful to memorize the common irregular plurals, for many words you simply have to know and understand that it is an irregular plural as a result of speaking and hearing English.

Non-Count Nouns

Non-count nouns, also called collective nouns, have no plural form because they are assumed to be plural. Most abstract nouns are non-count nouns. Some examples are:

Hair
Grass
Mud
Dress (when referring to a style of dress, not when referring to a clothing item that hangs in your closet)

If you are talking about multiple varieties or types of these irregular plurals, you cannot make them plural by adding an "s" or "es" to the end. Instead, you need to make them plural by adding a descriptive phrase. For example:

There are many different styles of hair
There are several varieties of grass
There are three different kinds of mud
The ancient people had a few types of styles of dress

Unchanging Nouns

Certain other nouns have the same plural form as singular form. A large number of animals happen to follow this rule. For example:

Deer is "deer" whether singular or plural
Fish is "fish" whether singular or plural
Bison is "bison" whether singular or plural
Moose is "moose" whether singular or plural
Elk is "elk" whether singular or plural.

Other Irregular Plurals

In addition to non-count nouns and unchanging nouns, there are several different types of irregular plurals which follow a pattern in the English language.

For most nouns that end in "f" or "fe," you drop the "f" or "fe" and add "ves"

Knife = knives
Wife = wives
Half = halves
Loaf = loaves

For many words that end in "us," change the "us" to an "i" (especially if it comes from a Latin word). There are exceptions to this rule and it is becoming more acceptable to add "es" instead of changing to "i."

Cactus = cacti
Fungus = fungi
Syllabus = syllabi

For nouns that end in "o" you add either "s" or "es". (Generally, most nouns ending in "o" just add "s" to make the plural, especially if there's a vowel before the final "o")

Zoo = zoos
Studio = studios
Tomato = tomatoes
Potato = potatoes
Some words ending in "o" can be spelled either way
Banjo = banjos or banjoes
Flamingo = flamingos or flamingoes

For many words that end in "is," change the "is" to an "es"

hypothesis = hypotheses
oasis = oases
crisis = crises

Nouns that end in "um" often become plural by changing "um" to "a"

bacterium = bacteria
medium = media
curriculum = curricula

Words that Change Form

Certain words do not add a letter to the end but instead, change the word itself. These words simply need to be memorized. Some examples include:

Man to men
Foot to feet
Tooth to teeth
Goose to geese

The best way to learn and understand irregular plurals is to practice speaking the English language, to read a great deal, to pay attention to words and phrases that you see and hear and to assemble a list of words with irregular plurals so you can begin to understand how to make each noun plural correctly.

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Irregular Plural Nouns

By YourDictionary

The vast majority of nouns in the English language are made plural by adding an "s" or "es" to the end of the word. For example, book, apple, house, table, door, cat, bush, boss are just some of the many words that become plural with the simple addition of an "s" or "es" (books, apples, houses, tables, doors, cats, bushes, bosses).However, certain nouns have irregular plurals which do not behave in this standard way and, even though most irregular plurals follow a pattern, there are always exceptions to watch out for.