What is the example of iregular noun?

A regular plural is a noun to which an -s or an -es is added to the end of the Word to form the plural.

An irregular noun is a noun that forms the plural in some other way. Examples of irregular plural nouns:

singular / plural

• mouse / mice
• company / companies
• man / men
• woman / women
• child / children
• person / people
• goose / geese
• ox / oxen
• foot / feet
• tooth / teeth
• cactus / cacti
• alumnus / alumni
• medium / media
• knife / knives
• wife / wives
• baby / babies
• memory / memories
• alumnus / alumni
• bacterium / bacteria
• pony / ponies