Irregular Plural Nouns in English: Rules, Patterns, and Examples

Irregular plural nouns do not follow the standard rule of adding -s or -es to form the plural. Instead, they change spelling in different ways—or sometimes do not change at all. Because there is no single plural rule for these nouns, grouping them by common patterns makes them much easier to learn and remember.

Irregular Plural Nouns

An irregular plural noun is a noun whose plural form is created by a spelling change rather than simply adding -s or -es.

For example:

• man → men
• woman → women
• child → children

Common Patterns of Irregular Plural Nouns

Although these nouns are called “irregular,” many of them follow recognizable patterns.

Vowel Change Inside the Word

Singular	Plural
man	men
woman	women
foot	feet
tooth	teeth
goose	geese
mouse	mice

Nouns Ending in -f / -fe → -ves

Singular	Plural
leaf	leaves
wolf	wolves
knife	knives

Note: Not all nouns ending in -f or -fe follow this rule. Common exceptions include roof → roofs, belief → beliefs, and chef → chefs.

Nouns with No Change in Plural Form

Singular	Plural
sheep	sheep
fish	fish
aircraft	aircraft
series	series
swine	swine

Note: The plural fishes is used when referring to different species of fish, especially in scientific or descriptive contexts.

Latin and Greek Origin Nouns

Singular	Plural
crisis	crises
analysis	analyses
diagnosis	diagnoses
datum	data
curriculum	curricula
index	indices
apex	apices
larva	larvae
genus	genera
erratum	errata

Special Irregular Forms

Singular	Plural
child	children
person	people
ox	oxen

Alumni Forms

Singular	Plural
alumnus (male)	alumni
alumna (female)	alumnae

Irregular Plural Nouns in Context

• The children are playing in the garden.
• Several mice were found in the kitchen.
• She brushed her teeth before going to bed.
• New scientific data support the theory.
• The university invited its alumni to the annual reunion.
• The shepherd is watching over a flock of sheep.
• This aquarium displays many different fishes from around the world.

Last Updated on January 22, 2026