Irregular Plurals of Nouns

Introduction

Although most nouns have plurals formed according to regular rules, some nouns have unusual, or irregular plurals. This article 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  knives life  lives wife  wives
Ends with -f	Change f to v then Add -es	half  halves wolf  wolves loaf  loaves
Ends with -o	Add -es	potato  potatoes tomato  tomatoes volcano  volcanoes
ends with -us	Change -us to -i	cactus  cacti nucleus  nuclei focus  foci
ends with -is	Change -is to -es	analysis  analyses crisis  crises thesis  theses
ends with -on	Change -on to -a	phenomenon  phenomena criterion  criteria
ALL KINDS	Change the vowel or Change the word or Add a different ending	man  men foot  feet child  children person  people tooth  teeth mouse  mice
Unchanging	Singular and plural are the same	sheep deer fish (sometimes)