In modern English, pronouns can function as substitutes for both proper and common nouns. For example, me, you, he, they, this, myself and themselves are all pronouns. Within functional linguistics, however, pronouns are described as a separate set of words, since pronouns in English have additional functions beyond those of ordinary nouns; for instance the pronoun who has an objective case, whom, whereas ordinary nouns in English no longer take this case. In this way, pronouns should not be seen as simple substitutes for full nouns, as these examples show:
'*' indicates that what follows is unacceptable in the exemplifying language. In the two examples above, no pronoun can occupy the position filled by Fred.