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 take an 's' in the plural form while uncountable nouns do not change form. It provides examples of nouns that can be either countable or uncountable depending on meaning. The document also discusses nouns that are always plural, nouns ending in 's', group nouns, two-part nouns, and plural forms of uncountable nouns. It concludes with examples of common plural mistakes made by students and exercises to identify and correct such mistakes.