There are 9 parts of speech or word classes in English language:
– nouns
– pronouns
– determiners
– verbs
– prepositions
– adjectives
– adverbs
– conjunctions
– interjections

Nouns are a group of words that we use to name:
– people: man, woman, teacher, John, Mary
– animals: cat, rabbit, horse, elephant
– plants: palm tree, coconut trees, grass, wheat, corn
– places: home, office, town, village, England
– concrete objects: chair, table, ball, water, money, sugar
– abstract objects: truth, lies, happiness, sorrow, time, friendship

Pronouns replaces nouns so that we don’t have to repeat them over and over again.

Do you like the manager?
I don’t like the manager.
The manager is not friendly.
(‘The manager’ is a noun phrase.)

By using pronouns, we can say:
Do you like the manager?
I don’t like him.
He is not friendly.

Do you know Jane?
I have a letter for Jane.
Please give this letter to Jane.
(‘Jane’ is a noun.)

By using pronouns, we can say:
Do you know Jane?
I have a letter for her.
Please give it to her.

There are 8 types of pronouns:
– Personal Pronouns
– Demonstrative Pronouns
– Possessive Pronouns
– Interrogative Pronouns
– Reflexive Pronouns
– Reciprocal Pronouns
– Indefinite Pronouns
– Relative Pronouns

We use interrogative pronouns to ask questions.
Interrogative pronouns replace the things we do not know.

Person
subject: who
object: whom

Animal/thing
subject: what
object: what

Person/thing
subject: which
object: which

Person
subject: whose
object: whose

John told me about the meeting.
John = subject
Who told you?
Who = interrogative pronoun asking the subject

I told Mary about the meeting.
Mary = object
Whom did you tell?
Whom = interrogative pronoun asking the object

An accident happened.
an accident = subject
What happened?
What = interrogative pronoun asking the subject

I want coffee.
coffee = object
What do you want?
What = interrogative pronoun asking the object

There are three cars. The BMW came first.
the BMW = subject
There are three cars. Which came first?
Which = interrogative pronoun asking the subject

There are two patients. The doctor will see the older patient first.
the older patient = object
There are two patients. Which will the doctor see first?
Which = interrogative pronoun asking the object