This document discusses common mistakes made with plural nouns in English. It begins by explaining the difference between countable and uncountable nouns, and how countable nouns typically take an 's' in the plural form. It provides examples of nouns that can be either countable or uncountable depending on the context. The document also discusses nouns that are always plural, nouns ending in 's', group nouns, two-part nouns, and expressions that are commonly mistaken as plural when they should remain singular. It concludes with exercises for the reader to identify and correct plural noun mistakes in sample sentences.