Pronouns can adopt the position of a noun or a noun phrase (NP). The context shows the reference of the pronoun to the rest of the sentence. There are eight classes of pronouns:
1) personal pronouns (I, you, they, it)
2) demonstrative pronouns (this, that)
3) reflexive pronouns (yourself, themselves)
4) reciprocal pronouns (each other)
5) possessive pronouns (theirs, mine)
6) indefinite pronouns (anybody)
7) relative pronouns (who, which)
8) interrogative pronouns (what, who)
The examples in brackets are not complete!
We will have a look at personal pronouns. This class refers to the speaker, the addressee and other entities.
In late Middle English the personal pronoun system changed. Instead of four cases (nominative, genitive, dative, accusative) there were only three cases left: nominative (e.g.: he), genitive (e.g.: his), oblique (e.g.: him). The oblique form consisted of a mixture of the former dative and accusative functions.
Within the pronoun system two changes took place. The first alteration was the morphological change of the neuter his into its. The second changing was a pragmatic one and concerned the second person. There, a loss of the differentiation between singular and plural occurred.