In this tutorial, you will learn how to create the plural form of regular nouns. You will also learn about irregular plurals.
Some nouns follow a pattern, or a set of rules to change into their plural form; these are regular plurals. However, there are always exceptions. In addition, there are also other nouns that do not follow a pattern. In their plural form, some of these words change completely, and some other words do not change at all; these are irregular plurals.
Source: Grammar Success 1