Plural nouns are used to refer to more than one person, place, thing, or idea. To form the plural of most nouns, simply add '-s' or '-es' to the end of the word. Examples of sentences using plural nouns include: 'The children are playing in the park,' 'I bought several books at the bookstore,' and 'The dogs barked loudly at the mailman.' Understanding how to use plural nouns correctly is essential for clear and accurate communication in English.