Topic summary
Nouns

Extracted from the Wikipedia article Noun.
Pronouns
Nouns and noun phrases can typically be replaced by pronouns, such as he, it, she, they, which, these, and those, to avoid repetition or explicit identification, or for other reasons (but as noted earlier, current theory often classifies pronouns as a subclass of nouns parallel to prototypical nouns). For example, in the sentence "Gareth thought she was weird", the word she is a pronoun that refers to a person just as the noun Gareth does. The word one can replace parts of noun phrases, and it sometimes stands in for a noun. An example is given below: