In this guide
The topic sentence is the most important sentence in a paragraph. It tells the reader what the paragraph is about, and it tells the writer what belongs in the paragraph and what doesn't.
If your child's paragraphs wander off topic, the problem often starts here.
What is a topic sentence?
A topic sentence states the main idea of a paragraph. It's usually the first sentence. Everything else in the paragraph should support it.
Think of it like the title of a mini-chapter. If someone read only the topic sentences of an essay, they should understand the main points.
A simple formula
For kids just learning, this formula works well:
Topic + what you want to say about it = topic sentence
| Topic | What I want to say | Topic sentence |
|---|---|---|
| Recess | it helps kids learn | Recess helps kids learn better in the afternoon. |
| Winter | it's the best season for families | Winter is the best season for family fun. |
| My grandmother | she taught me to be patient | My grandmother taught me how to be patient. |
The "what I want to say" part is what makes it a topic sentence instead of just a topic.
Weak vs. strong topic sentences
Too broad: Animals are interesting.
Stronger: Octopuses are some of the cleverest animals in the ocean.
Just a fact: Soccer is played with a ball.
Stronger: Soccer teaches kids how to work as a team.
Announcing: This paragraph is about my dog.
Stronger: My dog, Pepper, is the funniest member of our family.
A strong topic sentence makes a point that the rest of the paragraph can explain or prove. "This paragraph is about..." is a common habit in Grades 4–5; gently replace it with a sentence that says something.
Topic sentences in different kinds of writing
Opinion writing: the topic sentence is a reason. "One reason schools should have longer recess is that kids focus better after playing."
Informational writing: the topic sentence introduces a fact category. "Bees help plants in three important ways."
Narrative writing: topic sentences are less formal, but each paragraph still has a focus. "The trouble started as soon as we reached the campsite."
The checking question
After your child writes a paragraph, ask them to read the topic sentence and then each other sentence, one at a time. For each one, ask: "Does this sentence help explain or prove my topic sentence?"
If the answer is no, the sentence either belongs in a different paragraph or should be cut. This one habit fixes a large share of paragraph problems.
Practice activities
Guess the topic sentence. Read a paragraph from a non-fiction book aloud, leaving out the first sentence. Ask your child to write what they think the topic sentence was.
Topic sentence from details. Give three details ("Leaves change colour. Apples are ready to pick. The air feels cool.") and ask for a topic sentence that ties them together.
Make it stronger. Write three weak topic sentences and challenge your child to upgrade each one using the formula above.
Try it: Write a topic sentence for a paragraph about why your family should get a pet, and another for a paragraph about your favourite place.
Next step
Once topic sentences are solid, writing a complete paragraph becomes much easier. In an essay, the introduction holds a bigger version of the topic sentence, called the thesis or main opinion. See our guides on opinion essays and the five-paragraph essay.