Plural nouns are formed by adding an "-s" to the end of the word.

ball → balls
house → houses
book → books

Irregular plural nouns have different rules. Here are some rules for irregular plural nouns.

Word	Rule	Plural Form Example
Ends in ch, sh, x, o, ss	word+es	class-classes
Ends in y	word-y+ies	puppy-puppies
Ends in f	word-f+ves	loaf-loaves
Word with “oo”	change “oo” to “ee”	foot-feet

Abstract nouns name things you cannot touch or see. For example, the words love, hope, joy, laughter are abstract nouns.

Many abstract nouns are formed by adding a prefix to a concrete noun. A concrete noun names things you can touch or see, like a book.

For example: friend+ship =friendship, child+hood=childhood.