In the english langvage words can be named under any one of the eight parts of speech . These words are not  categorized per say , but their usage is classified into eight parts of speach such as noun , verb , prounoun adjective , adverb, preposition, conjuction and interjection.

1. Noun - According to David Green " A noun may be defined as the name of a person place or thing . By thing we mean something that can be seen and touched concerete or something that can only be through of and not seen and touched (abstract). The words that identify the who's where's and what's in a langvage is a noun . Nouns name persons, places, things and feelings . This is better understood with the following example . Lisa and tim were selling Lemonade in the park.

a. Who were selling? so the words Lisa and Tim are nouns (name)

b.Where were they selling? In the park- So park is a noun .(Place)

c What did they sell? lemonade. So lemonade is a noun (thing)

Functions of noun-  In a sentence the nouns can function as subjects, objects , and complements.

a Richie Rich would throw lavish parties and  invite his friends to his Dollar Mansion.

Richie Rich- Subject for verb 'throw' and 'invite'(door of the action)

b Richie Rich offered jughed two burgers to clean up the mess .

jughed- indirect object of 'offered'(indirect receiver)

Burgers- the direct object of 'offered'(direct receiver)