Singular & Plural Nouns | How to Form Regular Plural Nouns in English | Irregular Plural Noun Rules

Irregular Plural Nouns

Irregular plural nouns are nouns that do not become plural by adding -s or -es, as most nouns in the English language do. You’re probably familiar with many of these already. For example, the plural form of man is men, not mans. The plural form of woman is women, not womans. There are hundreds of irregular plural nouns, and in truth, you must memorize them through reading and speaking. There are, however, some common patterns to look out for.
we will explore the different types of irregular plural nouns in this kids zone video.

The most common irregular plurals
* Nouns ending in –f and –fe
To make a plural of a word ending in -f, change the f to a v and add es. Similarly, if a word ends in -fe, change the f to a v and add an s. The result for both types is a plural that ends in -ves. This spelling arose because of the difficulty of pronouncing f and s together in English (an attempt to do this will produce a v sound).

Singular (-f, -fe) Plural (-ves)
knife knives
life lives
wife wives.
Exceptions: roofs and proofs (among others).

* Nouns ending in -o
Plurals of words ending in -o are usually made by adding -es.

Singular (-o) Plural (-oes)
potato potatoes
hero heroes.
But of course, there are exceptions. (Aren’t there always?) Some words ending in -o that are borrowed from other languages take only an s to make a plural, such as pianos, cantos, photos, and zeros. Cello, which is an abbreviation of the Italian word violoncello, can be pluralized in the traditional way, as celli, or the commonly accepted anglicized way, as cellos.

Nouns that change vowels
* Many English words become plural by changing their vowels, such as oo to ee or an to en.

Singular Plural (vowel change)
foot feet
tooth teeth
goose geese.

Irregular nouns that change substantially
* For a variety of historical reasons, some words change in spelling substantially when made plural.

Singular Plural
mouse mice
louse lice.

Irregular nouns that do not change at all
Some English nouns are identical in their singular and plural forms. Many of these are the names of animals.

Singular/Plural (no change)
sheep
fish.

* Nouns ending in -us
To make a word ending in -us plural, change -us to -i. Many plurals of words ending in -us have anglicized versions, formed by simply adding -es. The latter method sounds more natural in informal settings. If there is an anglicized version that is well accepted, this will be noted in the dictionary entry for the word you are using.

Singular (-us) Plural (-i)
focus foci (also focuses)
fungus fungi.

* Irregular formation of nouns ending in -is
Nouns with an -is ending can be made plural by changing -is to -es. Some people have a hard time remembering that the plural of crisis is crises and the plural of axis is axes, but crisises and axises are incorrect.

Singular (-is) Plural (-es)
axis axes (this is also the plural of ax and axe)
analysis analyses.

* Irregular formation of nouns ending in -on
These Greek words change their -on ending to -a.

Singular (-on) Plural (-a)
phenomenon phenomena.

* Irregular formation of nouns ending in -um
Words ending in -um shed their -um and replace it with -a to form a plural. The plurals of some of these words are far better known than their singular counterparts.

Singular (-um) Plural (-a)criterion criteria
bacterium bacteria
stratum strata.

* Irregular formation of nouns ending in -ix
Nouns ending in -ix are changed to -ices in formal settings, but sometimes -xes is perfectly acceptable.

Singular (-ex, -ix)

Plural (-ces, -xes)
index

indices (or indexes)
appendix
appendices (or appendixes, in a medical context)

vortex
vortices (or vortexes).

These rules for irregular plural nouns must simply be memorized, although it is helpful to understand the patterns first in order to master them. We also have information on the Grammarly blog about patterns for regular nouns.