A noun is a word that represents a person, place, thing, or idea. Nouns are one of the basic parts of speech in English and are used to name and identify objects, people, places, and concepts. Nouns can be singular or plural, and they can also be common or proper. Common nouns refer to general things, while proper nouns refer to specific names of people, places, or things. Nouns are essential in constructing sentences and conveying meaning in language.