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 Place Thing Idea

Mr. Bean My brother The President John Etc.

Home Canada Classroom Phoenix Etc.

Skateboards Cows Neptune Computers Etc.

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 career-ending concussions.

Topic Sentences

Your turn.

Topic: Animals

Brainstorm in your mind a couple of main ideas about animals.

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

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 plague-infested 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.