A relative pronoun can be the subject of its own clause.
 Subject Relative Pronouns: who, which, that
American football, which is the most popular sport In the UnitedStates, began at
HarvardUniversity.
In this pattern, who, which, and that can be either singular or plural. Make the verb agree with
the antecedent.
I have not read the magazine that is lying on the coffee table.
(The verb is lying is singular to agree with the singular antecedent magazine.)
I have not read the magazines that are lying on the coffee table.
{The verb are lying is plural to agree with the plural antecedent magazines.)
 Adjective clauses are either restrictive (necessary) or nonrestrictive (unnecessary).
Restrictive (necessary): no commas
The professor who teaches my biology class won a Nobel Prize two years ago.
Nonrestrictive (unnecessary): commas
Professor Jones, who teaches my biology class, won a Nobel Prize two years ago.
The following examples show you how to combine two sentences to make a new sentence
containing a subject pattern adjective clauses.
For People

Restrictive
who, that

People save time and energy. They use microwave ovens.
People who use microwave ovens save time and energy.
People that use microwave ovens save time and energy.

Nonrestrictive
who

Microwave cooking is not popular with most professional chefs. Professional
chefs say that fast cooking does not allow flavors to blend.
Microwave cooking is not popular with most professional chefs, who say that
fast cooking does not allow flavors to blend.
For Animals and Things

Restrictive
that

Ovens are capable of cooking food quickly. They use microwave energy.
Ovens that use microwave energy are capable of cooking foods quickly.

Nonrestrictive
which

An electron tube in the oven produces microwaves. Microwaves cook by
agitating the water molecules in food.
An electron tube in the oven produces microwaves, which cook by agitating
the water molecules in food.

- You may delete the relative pronoun and the be verb when:
1. they are followed by a prepositional phrase.
Ex1: The man who is in the house is my father.
 The man in the house is my father.
Ex2: The books that are on the desk are mine
 The books on the desk are mine.
2. the main verb in the relative clause is progressive.
Ex1: The man who is swimming in the lake is my father.
The man swimming in the lake is my father.

Ex2: The books that are lying on the floor are mine.
 The books lying on the floor are mine.
3. the main verb in tenses
Ex1: People who buy lottery tickets are often found at bingo.

 People buying lottery tickets are often found at bingo.

Ex2: The bus which leaves at 6:03 was late today, so I caught the 6:08 one for downtown.

 The bus leaving at 6:03 was late today.