Pronouns are words like he, she, or you that let us cross-reference another entity somewhere else in the discourse or in the real world. Traditional grammars state that pronouns replace nouns, but it would be more accurate to say that they replace noun phrases.

(12a) [The airplane parked on the tarmac] appeared damaged.
(12b) It appeared damaged.

In (12b), the pronoun it does not replace just the word airplane of (12a); it replaces the entire string of words, the airplane parked on the tarmac. Replacing only airplane with a pronoun yields an ungrammatical sentence:

(12c) *The it parked on the tarmac appeared damaged.

Pronouns serve the same functions in a sentence that nouns do, most notably they are the heads of noun phrases. They largely observe the same syntactic rules as nouns, for example subject-verb agreement. For these reasons, we will consider pronouns to be a special type of noun rather than an independent word category.

We will use the term referent for the entity to which the pronoun refers. The referent does not necessarily have to be named linguistically. For example, if you and I are standing on a street corner and observe an automobile weaving in and out of traffic at a high rate of speed, you might say to me, "He's driving recklessly." The context of the situation tells me that the referent for he is the car's driver without your needing to use that noun phrase. However, pronouns often do refer to other noun phrases, and in this common situation those noun phrases are called antecedents.

Sometimes, we will need to note what pronoun refers to what antecedent. In this case, we will use a subscript notation. For example:

(13) Genevieve helped Albertj with hisj physics homework.

In (13), the letter j indicates that the pronoun his refers to Albert. In other words, j serves as a co-referencing variable. We can use such subscripts to make assertions about particular interpretations of pronouns. For example:

(14) *Genevievej made herj a sandwich.

We mark (14) as ungrammatical not because it has no sensible interpretation but because her cannot be understood to apply to Genevieve. If her referred to any female other than Genevieve, the sentence would be acceptable.

Pronouns come in several varieties:

Personal pronouns
I, you, he, she, etc. usually refer to a previously mentioned noun phrase or to a clearly implied person.
Reflexive pronouns
myself, yourself, themselves, etc. most commonly refer to the subject of the clause they are in.

(14) The graduating seniorsj threw themselvesj a party.

Because of this requirement that reflexives refer to the subject, reflexive pronouns usually cannot appear in subject position

(15) *Himself went to the party.

For the same reason, transitive verbs with reflexives in the direct object cannot be made passive:

(16a) Ron Howard cast himself in his own movie
(16b) *Himself was cast by Ron Howard in his own movie.

Indefinite pronouns:
somebody, anyone, everything, nothing, etc. don't refer to specific nouns.
Interrogative pronouns:
what, who, or whom, replace a noun phrase in forming a question.
Relative pronouns:
who, whom, which, whose, replace a noun phrase in a relative clause.

Interrogative and relative pronouns occur as parts of more complex structures, which we will study in a later chapter.