Use

Most plural nouns are formed by adding -s, but some plural nouns are irregular.

Example:

The wives have many scarves.

Explanation:

Wives and scarves are irregular plural nouns because they are not formed by simply adding -s to the end of the singular noun.

How to build

Here are some rules to follow to form irregular plural nouns:

If the noun ends with -fe, change the ‘f’ to ‘v’ and then add -s:

• knife → knives

If the noun ends with -f, change the ‘f’ to ‘v’ and then add -es:

• wolf → wolves

If the noun ends with -o, add -es:

• potato → potatoes

If the noun ends with -us, change the -us to -i:

• cactus → cacti

If the noun ends with -is, change the -is to -es:

• analysis → analyses

If the noun ends with -on, change the -on to -a:

• phenomenon → phenomena

Some irregular plural nouns do not follow any of these rules.

Sometimes, we change the vowel:

• foot → feet

Other times, we add a different ending:

• child → children

Sometimes, we change the word altogether:

• person → people