What’s a Main Idea?
Understanding Paragraph Structure
Authored and designed by Barbara Belroy
© 2003
There are times when your
instructor will have you read a
paragraph and then ask you the
all-important question: What’s the
main idea?
The first thing you should know is
that in order to be called a
paragraph, a paragraph needs to be
about one topic
To find the topic ask yourself,
“In general, who or what is this
paragraph about?”
Read the following paragraph:
Pets are often an important part of people’s lives. Different
types of animals can be pets, ranging from reptiles to horses. One of the
most common pets is a dog. Dogs serve a variety of purposes for
humankind. One way dogs serve humans is they are great just for
companionship. Many an only child has bonded with his/her “Fido,”
thus having a willing and loyal friend to play with on a daily basis.
Additionally, dogs have served humans as work animals, corralling
sheep, conquering rats, and guarding the homestead. Finally, dogs also
assist people, for example, by leading the blind, alerting the deaf, and
alerting epileptics of impending seizures.
Now that you’ve read the preceding paragraph, ask
yourself the following question. See if you can answer it
in one word. (If you need to review the paragraph, click
on the back arrow.)
What is this paragraph about?
Your answer should have been
dogs
If you were correct—hooray! If not,
bear with me, and I’ll explain. Let’s
look at the paragraph again:
Pets are often an important part of people’s lives. Different
types of animals can be pets, ranging from reptiles to horses. One of
the most common pets is a dog. Dogs serve a variety of purposes for
humankind. One way dogs serve humans is they are great just for
companionship. Many an only child has bonded with his/her “Fido,”
thus having a willing and loyal friend to play with on a daily basis.
Additionally, dogs have served humans as work animals, corralling
sheep, conquering rats, and guarding the homestead. Finally, dogs
also assist people, for example, by leading the blind, alerting the deaf,
and alerting epileptics of impending seizures.
Let’s examine each sentence and see what’s going on:
“ Pets are often an important part of
people’s lives.”
Now ask yourself “Is this what that whole paragraph is
about? Is the writer telling me that pets are important?
The answer is “NO.” So this
cannot be the main idea. Let’s
look at the next sentence.
“Different types of animals can be pets, ranging
from reptiles to horses.”
Is the whole paragraph trying to tell us
about pets ranging from reptiles to
horses?
NO.
Look at the next sentence.
“One of the most common pets is a dog.”
Is the whole paragraph about how
common dogs are?
No.
Let’s look at the next sentence.
“Dogs serve a variety of purposes for humankind.”
Does the paragraph tell us about the
different purposes dogs serve for
humankind?
YES!
Because the whole paragraph is telling us about the variety of purposes
dog serve for humankind, that’s the main idea!
Now examine the rest of the paragraph:
One way dogs serve humans is they are great just for
companionship. Many an only child has bonded with his/her “Fido,”
thus having a willing and loyal friend to play with on a daily basis.
Additionally, dogs have served humans as work animals, corralling
sheep, conquering rats, and guarding the homestead. Finally, dogs also
assist people, for example, by leading the blind, alerting the deaf, and
alerting epileptics of impending seizures.
You probably noticed that the rest of the
paragraph gave us specific information about the
variety of purposes dogs serve for humankind.
Those sentences are called supporting details
because the support (or prove) the main idea.
Now let’s analyze this paragraph—in other
words, let’s look at how this paragraph is
organized.
Main Idea: Dogs serve a variety of
purposes for humankind.
1. One way dogs serve humans is they are
great just for companionship.
2. Additionally, dogs have served humans
as work animals,
3. Dogs also assist people,
You probably noticed that the main idea is
supported by three (3) points. Click on the
back button to take another look.
Those three points are called major
supporting details because they are the
major details that support or prove the
main idea.
Let’s look at this organization
another way:
• Main Idea Dogs serve a variety of
purposes for humankind
Maj. SD. 1
Maj. SD 2
One way dogs
Additionally,
Serve humans is
dogs have
They are great
served humans
For companionship as work animals
Maj. SD3
Dogs also assist
people
But is that all that’s necessary for a good
paragraph? -- just a main idea and two or three
major supporting details?
Let’s see how this would look as a paragraph:
Dogs serve a variety of purposes for humankind.
One way dogs serve humans is they are great just for companionship.
Additionally, dogs have served humans as work animals. Finally, dogs
also assist people.
How’s that for a paragraph! Kinda short, huh? It’s wellorganized, but it needs something more.
What this paragraph needs is something called
“minor” supporting details.
Remember the “major” supporting details?
One way dogs serve humans is they are great
just for companionship.
Additionally, dogs have served humans as
work animals.
Dogs also assist people.
Well, each of these supporting details needs
more explanation and/examples.
Watch how major and minor supporting details make up the
parts of a paragraph. If I said to you, “Hey, dogs serve a
variety of purposes for humankind,” and then I walked
away, you’d be left with some questions, like “well, what
are these purposes?”
The major supporting details answer this question.
Me: Dogs serve a variety of purposes for
humankind.
You: Well, what are these purposes?
Me: They are great for companionship, they serve
as work animals, and they assist people.
Now you might ask the question, “How? How are they
great for companionship, how do they serve as work
animals, and how do they assist people?”
The minor supporting details answer these questions:
MAJOR SD 1 One way dogs serve humans is they are great just
for companionship. Minor SD Many an only child has bonded
with his/her “Fido,” thus having a willing and loyal friend to play
with on a daily basis. MAJOR SD 2 Additionally, dogs have
served humans as work animals, Minor SD corralling sheep,
Minor SD conquering rats, and Minor SD guarding the
homestead. MAJOR SD 3 Finally, dogs also assist people, for
example, by Minor SD leading the blind, Minor SD alerting the
deaf, and Minor SD alerting epileptics of impending seizures.
Let’s look at the layout again:
• Main Idea Dogs serve a variety of purposes for
humankind
Maj. SD. 1
Maj. SD 2
Maj. SD3
One way dogs
Additionally,
Serve humans is
dogs have
They are great
served humans
For companionship as work animals
Minor SD
Minor SD
Only child…
corral sheep
conquer rats
guard homestead
Dogs also
assist people
Minor SD
lead the blind
alert the deaf
alert for seizures
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