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 covers nouns that are always plural, nouns ending in 's', group nouns, two-part nouns, and mistakes students often make with plural forms. Exercises are provided to practice identifying and correcting plural noun errors.