This document discusses common mistakes made with plural nouns in English. It explains that there are two types of nouns: countable nouns, which can be pluralized by adding "s", and uncountable nouns, which cannot be pluralized. Some nouns can be both countable and uncountable depending on the context. The document provides examples of nouns that are always plural or end in "s" but are still singular. It concludes by correcting some common mistakes with plural nouns.