Topic Sentences
T + MI = TS
• T = Topic (usually a noun)
• MI = Main Idea (something about that noun)
• TS = Topic Sentence
A topic sentence is a sentence that contains a
topic, and something about that topic (called
the main idea).
A good topic sentence is a sentence that
contains a specific topic, a specific main idea
and grabs the readers interest.
Topic
Any noun can be a topic (a noun is a person,
place, thing or idea).
Person
Mr. Bean
My brother
The President
John
Etc.
Place
Home
Canada
Classroom
Phoenix
Etc.
Thing
Skateboards
Cows
Neptune
Computers
Etc.
Idea
Beauty
Honor
Hope
Friendship
Etc.
Topics
What is the topic of each sentence below:
• Fred eats worms.
Fred
• The worms were eaten by Fred.
The worms
• The governor rides in a fancy limousine.
The governor
• Soccer is a sport played by many people, like
David Beckham.
Soccer
Main Idea
A main idea is something about a noun—it’s the
specific idea concerning a noun, often an action.
What is the main idea of each sentence below:
• Fred eats worms.
Eats worms
• The worms were eaten by Fred.
Get eaten
• The governor rides in a fancy limousine.
Rides in a limousine
• Soccer is a sport played by many people, like
David Beckham.
Played by lots of people
Main Idea
A main idea is something about a noun—it’s the
specific idea concerning a noun.
It’s tougher to come up with a list of main ideas
unless you have a topic picked out. So here’s a
topic: People. Here are some main ideas about
people:
• Some people have heart disease.
• People live in many different kinds of places.
• People who play sports risk injury.
Main Idea
A main idea is something about a noun—it’s the
specific idea concerning a noun.
You name some main ideas about people…
Topic Sentence
A good topic sentence should have a specific
topic (noun) and something specific to say
about that topic (main idea). For example,
earlier I said, “People who play sports risk
injury.” To make that more specific I could say:
• Professional football players can get
concussions.
Topic Sentence
The “people who play sports” has become the
more specific:
• professional football players
and “sports injuries” has turned into the more
specific:
• concussions
Topic Sentence
Can “Professional football players can get
concussions,” become even more specific?
• Quarterbacks in the NFL can get careerending concussions.
Topic Sentences
Your turn.
Topic: Animals
Brainstorm in your mind a couple of main ideas
about animals.
Topic Sentences
Some possible main ideas I had:
• Some animals are mammals.
• Animals need food to survive.
• Australia has animals that can’t be found on
any other continent.
Topic Sentences
Pick one main idea that you brainstormed.
I’m going to pick “Australia has animals that
can’t be found on any other continent.”
Topic Sentences
Now that you have a main idea, let’s make both
the topic, “Animals,” and the main idea more
specific.
What is an animal that fits with your main idea?
An animal that fits with my main idea is the
kangaroo.
Topic Sentences
Now that we have a specific animal for our main
idea, let’s see if we can make our main idea even
more specific for that animal.
Your ideas?
My idea for my animal is that kangaroos are
leaping marsupials.
Topic Sentences
Now that we have a lot of specific things about
the topic and main idea, we can actually write a
topic sentence.
Come up with a topic sentence based on
everything you have thought about so far for
your animal.
Here’s mine:
“The kangaroo is a leaping marsupial unique to
Australia.”
Topic Sentences
Sometimes you have to find a topic sentence in a
paragraph that you read. Here’s how:
1. Carefully read the entire paragraph.
2. Decide what the topic (a one word noun) of the
entire paragraph is about.
3. Figure out, in your own words, what the main
idea of the paragraph is.
4. Finally, look for a topic sentence in the
paragraph that has the main idea.
Practice Passages
Find the topic sentence in the paragraph below.
Passage 1
When oxygen comes in contact with most metals, they rust.
Aluminum is a special metal that does not rust. Instead, it
reacts with oxygen in a different way. It forms a tough
surface film that stops rust. Things that need to spend a lot
of time outside are often made of aluminum. This is why
people use aluminum to make cars and airplanes. It's can
also be used as a building material. However, aluminum
doesn’t have the strength of steel. When strength is
needed, even rusty steel is stronger than aluminum.
Passage 1 Answer
The topic of the paragraph (what the entire
paragraph is about) is aluminum.
The main idea (the specific thing about
aluminum) of the paragraph is that aluminum
doesn’t rust.
The topic sentence that contains the main idea
is: Aluminum is a special metal that does not
rust.
Practice Passages
Come up with your own topic sentence for this paragraph.
Passage 2
Scientists have discovered a spider which is remarkably
different from any other known spider. This spider,
named Micromegale debliemma, has only two eyes
where most spiders have six or eight. Unlike most
spiders, it does not have lungs but instead absorbs
oxygen through its skin. Just three one-hundredth of an
inch long, Micromygale is one of the world’s smallest
spiders.
Passage 2 Answer
The topic of the paragraph (what the entire
paragraph is about) is spiders.
The main idea (the specific thing about
aluminum) of the paragraph is that scientists
found a unique spider.
The topic sentence that contains the main idea
is: Scientists have discovered a spider which is
remarkably different from any other known
spider.
Practice Passages
Find the topic sentence in the paragraph below.
Passage 3
The Black Plague killed about one-third of Europe's whole
population from 1347-1351. The Black Plague was caused
because back then people knew almost nothing about germs or
sanitary conditions. They had no idea how the disease spread.
Rats ran everywhere. Fleas lived on the rats. These fleas carried
the deadly Black Plague germ. Just before the Plague broke out,
people had killed off a great many cats. Up until then the cats
had kept the rat population small. With fewer cats, there were
more rats than ever before. And every rat had the plagueinfested fleas in its fur.
Passage 3 Answer
The topic of the paragraph (what the entire
paragraph is about) is the Black Plague.
The main idea (the specific thing about
aluminum) of the paragraph is that rats helped
cause the black plague.
The topic sentence that contains the main idea
is: The Black Plague was caused because back
then people knew almost nothing about germs
or sanitary conditions.