This document discusses common mistakes made with plural nouns in English. It explains the differences between countable and uncountable nouns, and how countable nouns typically 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' that are singular, group nouns, two-part nouns, and exercises for students to practice correcting mistakes with nouns.