A noun is a word that names a person, place, thing, or idea. For example, in the sentence "The dog barked," the word dog is a noun because it identifies an animal. Nouns can be specific, like Sarah or Paris, or general, like teacher or city. They help us understand who or what we are talking about. Nouns can also be categorized into different types. Common nouns refer to general items, while proper nouns name specific ones. For instance, apple is a common noun, but Granny Smith is a proper noun. Understanding nouns is essential for building sentences and communicating clearly.