The word "noun" comes from the Latin nomen meaning "name." Word classes like nouns were first described by Sanskrit grammarian Painini and ancient Greeks like Dionysios Thrax, and defined in terms of their morphological properties. For example, in Ancient Greece, nouns can be inflected for grammatical case, such as dative or accusative. Verbs, on the other hand, can be inflected for tenses, such as past, present or future, while nouns cannot. Aristotle also had a notion of onomata (nouns) and rhemata (verbs) which, however, does not exactly correspond our notions of verbs and nouns. In her dissertation, Vinokurova has a more detailed discussion of the historical origin of the notion of a noun.
A noun is a word used to refer to people, animals, objects, substances, states, events and feelings. Nouns can be a subject or an object of a verb, can be modified by an adjective and can take an article or determiner.
In traditional school grammars, one often encounters the definition of nouns that they are all and only those expressions that refer to a person, place, thing, event, substance, quality, or idea, etc. This is a semantic definition. It has been criticized by contemporary linguists as being quite uninformative. Part of the problem is that the definition makes use of relatively general nouns ("thing," "phenomenon," "event") to define what nouns are. The existence of such general nouns shows us that nouns are organized in taxonomic hierarchies. But other kinds of expressions are also organized in hierarchies. For example all of the verbs "stroll," "saunter," "stride," and "tread" are more specific words than the more general "walk." The latter is more specific than the verb "move." But it is unlikely that such hierarchies can be used to define nouns and verbs. Furthermore, an influential theory has it that verbs like "kill" or "die" refer to events, and so they fall under the definition. Similarly, adjectives like