A word used in place of a noun or noun phrase. This includes personal pronouns, possessive pronouns, relative pronouns and others.
Pronouns differ from nouns in that they have no intrinsic descriptive content, and so are functors. There are a range of different types of pronoun found in English, including the pronominal noun one(s) used in sentences like "I’ll take the red one(s)", pronominal quantifiers like any in "I couldn’t find any", and pronominal determiners like this in "This is hard". The term pronoun is most frequently used to indicate a class of items (like he/him/his) traditionally referred to as personal pronouns (though analysed in much recent work as pronominal determiners).