Irregular Plurals of Nouns

Introduction

Although most nouns have plurals formed according to regular rules (see Regular Plurals of Nouns), some nouns have unusual, or irregular plurals. This page will introduce the most common ones, so that you can learn them.

Types of irregular plural

There are many types of irregular plural, but these are the most common:

Noun type Forming the plural Example
Ends with -fe Change f to v
then
Add -s
knife arrow to the right knives
life arrow to the right lives
wife arrow to the right wives
Ends with -f Change f to v
then
Add -es
half arrow to the right halves
wolf arrow to the right wolves
loaf arrow to the right loaves
Ends with -o Add -es potato arrow to the right potatoes
tomato arrow to the right tomatoes
volcano arrow to the right volcanoes
ends with -us Change -us to -i cactus arrow to the right cacti
nucleus arrow to the right nuclei
focus arrow to the right foci
ends with -is Change -is to -es analysis arrow to the right analyses
crisis arrow to the right crises
thesis arrow to the right theses
ends with -on Change -on to -a phenomenon arrow to the right phenomena
criterion arrow to the right criteria
ALL KINDS Change the vowel
or
Change the word
or
Add a different ending
man arrow to the right men
foot arrow to the right feet
child arrow to the right children
person arrow to the right people
tooth arrow to the right teeth
mouse arrow to the right mice
Unchanging Singular and plural
are the same
sheep
deer
fish (sometimes)

When you are sure that you understand the lesson, you can continue with the exercises.