A noun is a word which names an object or entity such as a person, thing, place, substance, quality or idea.
A proper noun is used to name a specific person, place or thing. A proper noun is always capitalized. A common noun is used to name one or all members of a class or group. A common noun does not have to be capitalized. Common nouns can be concrete or abstract. A concrete noun is one which names a thing rather than a quality, state, action or concept. Concrete nouns are used to name things people can use their senses to see. An abstract noun is one which names a quality, state, action or concept. Abstract nouns are used to name intangible things such as qualities (sweetness) and ideas (freedom).