Finding the Main Idea
FoundationThe main idea is what the paragraph is mostly about — usually in the topic sentence, supported by details.
- The main idea = what the whole paragraph is mostly about, in one sentence
- The topic sentence is usually first; signal words like Unfortunately / However matter
- Details are support: numbers like over 400 million years and 500 species are not the main idea
文體小知識：Find the one sentence that rules the paragraph.
§Text Passage
1Sharks have lived in the oceans for over 400 million years, which means they are older than the dinosaurs. There are more than 500 different species, and they live in every ocean in the world. Some sharks are longer than a bus, while others are smaller than your school ruler. Most sharks are harmless to humans because they eat fish, seals and squid. Only about 10 species are dangerous, and attacks are very rare.
2Unfortunately, people kill millions of sharks every year for their fins. Fishermen cut off the fins and throw the sharks back into the sea. This has caused many populations to drop, and some species may disappear completely. Scientists warn that losing sharks will damage the whole ocean ecosystem, because sharks keep the number of smaller fish under control. Without them, the balance of nature will be destroyed.
3The good news is that everyone can help. We can refuse to eat shark fin soup at banquets and weddings. We can support the shops and restaurants that protect sea life. Several countries have already banned shark fishing in their waters, and Hong Kong has joined an international agreement to protect shark species too. We should protect sharks because they are important for the ocean ecosystem, and a healthy ocean is important for us all.
§Sentence-by-sentence translation Sentence-by-sentence translation
Sharks have lived in the oceans for over 400 million years, which means they are older than the dinosaurs.
鯊魚在海洋裡生活了超過四億年，即是牠們比恐龍還古老。
There are more than 500 different species, and they live in every ocean in the world.
鯊魚有超過五百個品種，在全世界每個海洋都找到牠們。
Some sharks are longer than a bus, while others are smaller than your school ruler.
有些鯊魚比一架巴士還長，有些就比你的學校間尺還小。
Most sharks are harmless to humans because they eat fish, seals and squid.
大部分鯊魚對人類無害，因為牠們吃魚、海豹同魷魚。
Only about 10 species are dangerous, and attacks are very rare.
只有大約十個品種是危險的，而且襲擊事件非常罕見。
Unfortunately, people kill millions of sharks every year for their fins.
可惜的是，人類每年為了魚翅殺死幾百萬條鯊魚。
Fishermen cut off the fins and throw the sharks back into the sea.
漁民割了魚鰭，就把鯊魚丟回海裡。
This has caused many populations to drop, and some species may disappear completely.
這個情況令很多族群數量下跌，有些品種還可能完全消失。
Scientists warn that losing sharks will damage the whole ocean ecosystem, because sharks keep the number of smaller fish under control.
科學家警告，失去鯊魚會破壞整個海洋生態系統，因為鯊魚控制住小魚的數量。
Without them, the balance of nature will be destroyed.
沒有了牠們，大自然的平衡就會被摧毀。
The good news is that everyone can help.
好消息是，人人都可以出一分力。
We can refuse to eat shark fin soup at banquets and weddings.
我們可以在宴會同婚禮上拒絕吃魚翅。
We can support the shops and restaurants that protect sea life.
我們可以支持一些保護海洋生物的商舖同餐廳。
Several countries have already banned shark fishing in their waters, and Hong Kong has joined an international agreement to protect shark species too.
有幾個國家已經禁止在自己水域捕鯊，香港亦加入了保護鯊魚品種的國際協議。
We should protect sharks because they are important for the ocean ecosystem, and a healthy ocean is important for us all.
我們應該保護鯊魚，因為牠們對海洋生態很重要，而健康的海洋對我們所有人都很重要。
1Summary 重點摘要
The main idea is what the paragraph is mostly about — usually in the topic sentence, supported by details.
2Vocabulary cards Vocabulary
The main message.
First sentence.
Supporting fact.
Prove main idea.
Short version.
A block of text.
Reading passage.
Important word.
3Step by step Steps
- Read first sentenceThe topic sentence usually comes first: Sharks have lived in the oceans for over 400 million years — at once you know the paragraph is about how old sharks are.
- Find key wordsRepeated words are clues: sharks, ocean, species keep coming back — the main idea is built on them.
- SummariseSay each paragraph in one line: P1 = sharks are being killed for their fins. Drop the numbers, keep the point.
- Idea vs detailNumbers are details, not the idea: over 400 million years, 500 species, only about 10 dangerous — they support the idea that most sharks are harmless.
- TransitionsUnfortunately and However mark the real point: Unfortunately, people kill millions of sharks for their fins. A writer's key message often sits after a transition.
- The umbrella testThe main idea must cover the whole paragraph: 'Sharks are old' is too narrow; 'The ocean is important' is too wide. Correct: We should protect sharks because they keep the ocean healthy.
- Paragraph jobsThree paragraphs: P0 sharks are harmless, P1 they are in danger, P2 how we can help. See the structure and the main idea appears.
4Diagrams Diagrams
5Worked example Example
Based on the shark passage, what is the main idea of the second paragraph (the one about hunting)? Answer in one complete sentence.
- Step 1: Read the first sentence — Unfortunately, people kill millions of sharks every year for their fins.
- Step 2: Circle the repeated key words — sharks, kill, drop, disappear.
- Step 3: Check that the other sentences support the first one — falling populations and disappearing species are results of the hunting.
- Step 4: Do the umbrella test — your main idea must cover every detail in the paragraph.
- Step 5: Answer in a full sentence — The main idea is that…
- Answer: The main idea is that people kill millions of sharks for their fins, and this is pushing many species towards extinction. The first sentence — Unfortunately, people kill millions of sharks every year for their fins — is the topic sentence, and the rest of the paragraph (populations drop, species may disappear) is supporting detail. One clear sentence is enough; do not copy the numbers.
6Common mistakes Mistakes
7Quick check Quick check
Q1Which sentence is the main idea of paragraph 1?
Q2Where is the topic sentence?
Q3What supports the main idea?
Q4What is a short version?
Q5What is a block of text?
Q6What is the main idea?
Q7How many shark species are dangerous?
Q8What should we do?
8Recap Recap
- The main idea = what the whole paragraph is mostly about, in one sentence
- The topic sentence is usually first; signal words like Unfortunately / However matter
- Details are support: numbers like over 400 million years and 500 species are not the main idea
- Umbrella test: the main idea must cover every detail — not too narrow, not too broad
- Message of the passage: sharks keep the ocean balanced — refuse shark fin soup