Relative Clauses — Mệnh đề quan hệvsComplex Sentence (Câu phức)

Reference map

Chọn relative pronoun từ danh từ được mô tả

1. 1
   Ngườiwho · that
2. 2
   Vật hoặc ýwhich · that
3. 3
   Sở hữuwhose
4. 4
   Nơi hoặc thời gianwhere · whennon-defining clause cần dấu phẩy và không dùng that

Tóm tắt

Decision flowchart — Defining hay Non-defining?

Hỏi: "Nếu bỏ relative clause, người nghe có XÁC ĐỊNH được noun này không?"

• CÓ (vẫn xác định được — relative clause chỉ thêm thông tin) → NON-DEFINING → DÙNG dấu phẩy → DÙNG "which" hoặc "who" (KHÔNG "that")
• KHÔNG (relative clause cần thiết để biết noun này là cái gì) → DEFINING → KHÔNG dấu phẩy → DÙNG "which/who/that"

Ví dụ: - "My brother, who lives in Hanoi, called me yesterday." (non-defining: chỉ có 1 anh trai → who lives in Hanoi chỉ thêm thông tin → CÓ phẩy) - "The book that I borrowed is interesting." (defining: nhiều sách → "that I borrowed" cần để biết SÁCH NÀO → KHÔNG phẩy)

Mệnh đề quan hệ (Relative Clause) là một mệnh đề phụ đứng ngay sau danh từ để bổ sung thông tin về danh từ đó. Nó được mở đầu bởi relative pronoun (who, which, that, whose, whom) hoặc relative adverb (where, when, why).

• The student who won the prize is from my class. (mô tả "student" nào)
• The book that I borrowed was very interesting. (mô tả cuốn sách nào)
• This is the city where I was born. (mô tả thành phố)

Tại sao quan trọng

Mệnh đề quan hệ cho phép kết hợp hai câu ngắn thành một câu phức, tạo ra văn phong học thuật và tự nhiên hơn. Trong IELTS Writing và Speaking, thiếu cấu trúc này sẽ giới hạn điểm Grammatical Range.

Relative Pronouns và Relative Adverbs

Từ	Thay thế cho	Chức năng	Ví dụ
who	người	chủ ngữ	The man who called you is my boss.
whom	người	tân ngữ (trang trọng)	The manager whom I met was helpful.
which	vật / ý	chủ ngữ hoặc tân ngữ	The car which I bought last year broke down.
that	người hoặc vật	chủ ngữ hoặc tân ngữ	The book that she recommended was amazing.
whose	sở hữu (người/vật)		The student whose work I read was talented.
where	nơi chốn		The city where I grew up has changed a lot.
when	thời gian		I remember the day when we first met.
why	lý do		That's the reason why I quit.

Who vs. Whom

• Who = chủ ngữ (subject) của mệnh đề quan hệ:
• The teacher who taught me English retired last year. (who = chủ ngữ: "who taught me")
• Whom = tân ngữ (object) — trang trọng, hay bị thay bằng "who" trong giao tiếp:
• The doctor whom I consulted recommended rest. (whom = tân ngữ: "I consulted whom")

That vs. Which / Who

• That dùng trong mệnh đề quan hệ xác định (defining relative clause)
• Which dùng trong mệnh đề quan hệ không xác định (non-defining) hoặc thay thế "that"
• That KHÔNG dùng trong non-defining clause

Loại 1: Defining Relative Clauses — Mệnh đề xác định

Cung cấp thông tin thiết yếu để xác định danh từ — không có dấu phẩy.

Nếu bỏ mệnh đề này, câu mất nghĩa hoặc không rõ đề cập đến ai/cái gì.

• The woman who lives next door is a nurse. (xác định người phụ nữ nào)
• I want to buy the car that/which is in the window. (xác định chiếc xe nào)
• Children who eat well tend to be healthier. (xác định nhóm trẻ em nào)

Có thể bỏ relative pronoun khi nó là tân ngữ của mệnh đề quan hệ:

• The book (that/which) I read was fascinating. (that/which = tân ngữ → có thể bỏ)
• The man (who/that) she married is very kind. (who/that = tân ngữ → có thể bỏ)
• The car (that) I bought broke down. ✅

Không thể bỏ khi relative pronoun là chủ ngữ: - The book that is on the table is mine. ✅ (that = chủ ngữ, không bỏ được)

Loại 2: Non-defining Relative Clauses — Mệnh đề không xác định

Cung cấp thông tin bổ sung (có thể bỏ mà không ảnh hưởng đến nghĩa chính) — có dấu phẩy cả hai đầu.

• My sister, who lives in London, is visiting next week. (đã biết tôi chỉ có một chị → thông tin thêm)
• The Eiffel Tower, which was built in 1889, is one of the most visited monuments in the world.
• Last summer, when I was in Paris, I visited several museums.

Luật quan trọng: - KHÔNG dùng "that" trong non-defining clause - KHÔNG bỏ relative pronoun trong non-defining clause - Luôn có dấu phẩy

❌ My sister, that lives in London, is visiting. (sai — dùng "that" trong non-defining) ✅ My sister, who lives in London, is visiting.

Whose — sở hữu

"Whose" thay thế cho 's hoặc his/her/its:

• I know a student. His work won first prize. → I know a student whose work won first prize.
• The company whose products I use has just launched a new app.
• She lives in a house whose roof is painted red.

Where, When, Why

• Where = in which / at which (nơi chốn):
• This is the school where I studied for ten years.

• This is the school in which I studied. (trang trọng hơn)

• When = at which / during which (thời gian):

• I remember the summer when we travelled across Europe.

• There are times when I feel overwhelmed.

• Why = for which (lý do — chỉ dùng sau "reason"):

• That's the reason why she left the company.
• That's the reason (why/that/∅) she left.

Rút gọn mệnh đề quan hệ (Reduced Relative Clauses)

Khi relative pronoun là chủ ngữ, có thể rút gọn bằng cách:

→ V-ing (khi mệnh đề ở thể chủ động): - The man who is standing at the door is my father. - → The man standing at the door is my father.

• Students who want to improve should practise daily.
• → Students wanting to improve should practise daily.

→ V3 (past participle) (khi mệnh đề ở thể bị động): - The letter that was written in French was hard to read. - → The letter written in French was hard to read.

• The report which was published last year has been updated.
• → The report published last year has been updated.

Lỗi thường gặp

Lỗi 1: Dùng "that" trong non-defining clause

• ❌ My brother, that is a doctor, lives in Hanoi.
• ✅ My brother, who is a doctor, lives in Hanoi.

Lỗi 2: Dùng lại đại từ sau relative pronoun (double pronoun)

• ❌ The student who he won the prize is from my class.
• ✅ The student who won the prize is from my class. (bỏ "he")
• ❌ The book which I read it was amazing.
• ✅ The book which I read was amazing. (bỏ "it")

Lỗi 3: Dùng "which" thay vì "whose"

• ❌ The company which products are famous worldwide...
• ✅ The company whose products are famous worldwide...

Lỗi 4: Quên dấu phẩy trong non-defining clause

• ❌ My mother who is 60 years old still works full time.
• ✅ My mother, who is 60 years old, still works full time.

Lỗi 5: Dùng "which" để thay toàn bộ mệnh đề (Sentence relative clause)

Có thể dùng "which" để bình luận về toàn bộ ý của mệnh đề trước — nhưng chỉ trong non-defining:

• She passed all her exams, which made her parents very proud.
• He refused to apologise, which surprised everyone.

✅ Cấu trúc này rất hữu ích cho IELTS Writing.

Ứng dụng trong IELTS

Writing Task 2 — thêm thông tin về chủ đề:

• Young people who grow up in cities often have more opportunities than those who live in rural areas.
• Technology, which has transformed every aspect of modern life, brings both benefits and challenges.
• The country whose economy grew fastest last decade is now facing new challenges.

Writing Task 1 — mô tả dữ liệu:

• The year when sales reached their peak was 2019.
• Countries where literacy rates are high tend to have stronger economies.

Speaking — mô tả người và nơi:

• She's the kind of person who always makes you feel welcome.
• It's a place where you can completely relax and forget about work.
• I remember a time when we had no internet and had to look everything up in books.

Bài tập luyện

Nối hai câu bằng mệnh đề quan hệ

1. The woman works at the airport. She helped us find our gate.
2. I live in a small town. The town has a beautiful old castle.
3. I have a friend. Her father is a famous artist.
4. 1990 was the year. I was born that year.
5. The report was very useful. I read the report yesterday.

Sửa lỗi

1. My car, that I bought last year, has already broken down.
2. The student who she won the prize is from Hanoi.
3. This is the city which I grew up in it.
4. He's someone which I really admire.
5. The man, whose lives next door, is a doctor.

Đáp án

Nối câu: 1. The woman who helped us find our gate works at the airport. 2. I live in a small town that/which has a beautiful old castle. 3. I have a friend whose father is a famous artist. 4. 1990 was the year when I was born / in which I was born. 5. The report (that/which) I read yesterday was very useful.

Sửa lỗi: 1. My car, which I bought last year, has already broken down. (non-defining → which, không phải that) 2. The student who won the prize is from Hanoi. (bỏ "she") 3. This is the city where I grew up / in which I grew up. (bỏ "in it") 4. He's someone who/whom I really admire. (người → who/whom, không phải which) 5. The man who lives next door is a doctor. (non-defining sai: nếu đây là mệnh đề xác định → không dấu phẩy; nếu non-defining → The man next door, who is a doctor, ...)

Tóm tắt nhanh

Relative pronouns: - who → người (chủ ngữ) - whom → người (tân ngữ, trang trọng) - which → vật - that → người hoặc vật (chỉ dùng trong defining clause) - whose → sở hữu

Relative adverbs: - where → nơi chốn | when → thời gian | why → lý do (sau "reason")

Hai loại:

	Defining	Non-defining
Dấu phẩy	Không	Có
"that"	Được	Không được
Bỏ được không	Bỏ được (nếu là object)	Không bỏ được
Ý nghĩa	Thiết yếu	Bổ sung

Rút gọn: relative pronoun (subject) + be → bỏ hết; hoặc dùng V-ing / V3

Clause hierarchy

Mệnh đề phụ phải bám vào một mệnh đề chính

1. 1
   SubordinatorAlthoughbáo hiệu quan hệ nhượng bộ
2. 2
   Dependent clausepublic transport is crowded
3. 3
   Main clausemany commuters still use itphần có thể đứng độc lập

Tóm tắt

Complex sentence = một independent clause (mệnh đề chính) + ít nhất một dependent clause (mệnh đề phụ), nối bằng subordinating conjunction (because, although, when, if, since, unless...) hoặc relative pronoun (who, which, that, where).

Tại sao quan trọng

Complex sentences là cấu trúc bắt buộc cho điểm cao trong IELTS:

IELTS Band	Đặc điểm cấu trúc câu
Band 5	Chủ yếu simple sentences, một số compound
Band 6	Dùng được compound sentences, bắt đầu có complex
Band 7	Dùng thành thạo complex sentences với variety
Band 8–9	Complex sentences phong phú, linh hoạt, ít lỗi

Theo Band Descriptors của IELTS, Band 7 yêu cầu: "uses a variety of complex structures". Không có complex sentences = không thể đạt Band 7.

Trong IELTS Writing Task 2: - ❌ Band 5: "There are many benefits of technology. Technology helps communication. It also helps education." - ✅ Band 7: "Although technology has transformed communication, its impact on education —especially in areas where access is limited— is still debated by researchers who emphasise the importance of equal opportunity."

Định nghĩa

Independent Clause (Main Clause)

Mệnh đề có thể đứng độc lập thành câu hoàn chỉnh: - The economy grew. - Students work hard. - Governments should invest in education.

Dependent Clause (Subordinate Clause)

Mệnh đề có S + V nhưng không đứng độc lập được vì bắt đầu bằng từ nối phụ: - because the economy grew → cần câu chính - although students work hard → cần câu chính - who invented the telephone → mô tả noun, cần câu chính

Complex Sentence

[Independent Clause] + [Dependent Clause] hoặc [Dependent Clause] + [Independent Clause]

(Khi dependent clause đứng đầu câu, dùng dấu phẩy sau nó)

Cấu trúc

Loại 1: Adverb Clause (Mệnh đề trạng ngữ)

Bắt đầu bằng subordinating conjunction, mô tả điều kiện, thời gian, lý do, mục đích, kết quả, nhượng bộ...

Vị trí: - Cuối câu: không cần dấu phẩy - She succeeded because she worked hard. - Đầu câu: dùng dấu phẩy sau dependent clause - Because she worked hard, she succeeded.

Loại	Subordinating Conjunctions	Ví dụ
Lý do (Reason)	because, since, as	She left because she was tired.
Nhượng bộ (Concession)	although, though, even though, while, whereas	Although it was raining, they continued.
Điều kiện (Condition)	if, unless, provided that, as long as, on condition that	If governments invest, outcomes improve.
Thời gian (Time)	when, while, after, before, until, as soon as, once, whenever	When she arrived, the meeting had started.
Mục đích (Purpose)	so that, in order that	She studied so that she could improve.
Kết quả (Result)	so...that, such...that	It was so hot that no one went outside.
Tương phản (Contrast)	whereas, while	Whereas cities expand, rural areas shrink.

Loại 2: Relative Clause (Mệnh đề quan hệ)

Bắt đầu bằng relative pronoun (who, whom, which, that, whose, where, when), mô tả một danh từ trong câu.

Relative Pronoun	Dùng cho	Ví dụ
who / whom	Người (who = subject, whom = object)	The student who studied hardest passed.
which	Vật, ý tưởng	The book which I borrowed was excellent.
that	Người hoặc vật (restrictive)	The house that he built is still standing.
whose	Sở hữu (người hoặc vật)	The student whose work was outstanding won.
where	Nơi chốn	The city where I grew up has changed.
when	Thời gian	The year when she graduated was 2020.

Hai loại relative clause:

Restrictive (Defining): Cần thiết để xác định danh từ — không có dấu phẩy - The students who study regularly tend to do well. (không phải tất cả sinh viên — chỉ những em học đều)

Non-restrictive (Non-defining): Thêm thông tin, không cần thiết — có dấu phẩy - My sister, who lives in London, is a doctor. (ta đã biết ai là chị gái — thêm thông tin phụ)

Lưu ý: that không dùng trong non-restrictive clause — phải dùng which hoặc who. - ❌ My car, that I bought last year, is already broken. - ✅ My car, which I bought last year, is already broken.

Loại 3: Noun Clause (Mệnh đề danh từ)

Mệnh đề đóng vai trò như một danh từ trong câu — làm chủ ngữ, tân ngữ, hoặc bổ ngữ.

Vị trí	Từ nối	Ví dụ
Chủ ngữ	What, That, Whether	What matters most is consistent effort.
Tân ngữ	that, what, whether, how, why, when	I believe that education is a right.
Sau linking verb	that, what	The problem is that funding is limited.

Cách dùng phổ biến

1. Adverb clauses — Thể hiện lập luận logic

Diễn đạt nguyên nhân (Band 7+): - Since many young people lack financial literacy, banks should offer educational programs. (since = because, formal hơn) - As the population continues to age, healthcare systems face increasing pressure.

Diễn đạt nhượng bộ — công nhận ý đối lập (Band 7 signature): - Although social media has numerous benefits, its negative effects on mental health cannot be ignored. - Even though technology creates jobs, it also displaces many workers. - While some argue that globalization benefits all nations, evidence suggests otherwise.

Diễn đạt điều kiện — lập luận có điều kiện: - Unless governments take immediate action, climate change will become irreversible. - Provided that adequate funding is available, the project could be highly successful.

2. Relative clauses — Mô tả và hạn định danh từ

Thêm thông tin về người/vật: - Countries that invest heavily in education tend to have stronger economies. - The researchers whose findings challenged the consensus faced significant scrutiny.

Non-restrictive — thêm chi tiết không thiết yếu: - Finland, which consistently tops international education rankings, invests significantly in teacher training.

3. Noun clauses — Diễn đạt ý kiến, niềm tin

Đặc biệt hữu ích trong IELTS Writing khi nêu quan điểm: - I believe that stricter regulations are necessary to address this issue. - What concerns me most is the long-term economic impact. - *It is widely accepted that education is the foundation of development. - The question is whether governments should intervene* in the market.

4. Phối hợp trong một câu

Complex sentences có thể chứa nhiều dependent clauses: - Although the government introduced reforms that aimed to reduce inequality*, many economists argue that the measures were insufficient. - Although... reforms → Adverb clause (nhượng bộ) - that aimed to reduce inequality → Relative clause - that the measures were insufficient* → Noun clause

Dấu hiệu nhận biết

Nhận ra Dependent Clause → Complex Sentence

Loại	Từ mở đầu
Adverb clause	because, since, as, although, though, even though, while, whereas, if, unless, when, whenever, before, after, until, once, so that, provided that, as long as
Relative clause	who, whom, which, that, whose, where, when (sau danh từ)
Noun clause	that, what, whether, if, how, why, when, where (làm subject/object)

Quy tắc nhanh: Nếu thấy một trong các từ trên và sau nó là S + V → đó là dependent clause → câu chứa nó là complex sentence.

Ví dụ

Phân tích câu thực tế

Câu 1:

"Although governments have made considerable efforts to reduce carbon emissions, scientists warn that climate change is accelerating at an unprecedented rate."

• "Although governments have made considerable efforts to reduce carbon emissions" → Dependent adverb clause (nhượng bộ, bắt đầu bằng although)
• "scientists warn" → Independent clause chính
• "that climate change is accelerating at an unprecedented rate" → Dependent noun clause (tân ngữ của warn)
• → Complex sentence với 2 dependent clauses

Câu 2:

"The cities that experience the fastest economic growth are often those where inequality is most severe."

• "The cities...are often those" → Independent clause
• "that experience the fastest economic growth" → Relative clause (restrictive, mô tả cities)
• "where inequality is most severe" → Relative clause (mô tả those)
• → Complex sentence với 2 relative clauses

Ví dụ IELTS Writing Task 2

Band 5 (simple + basic compound):

"Social media has benefits. It connects people. But it also has problems. Young people spend too much time on it."

Band 7 (complex sentences):

"Although social media has revolutionised the way people communicate, enabling individuals who live in different countries to maintain close relationships, there is growing concern that excessive use is damaging young people's mental health. Since the brain is still developing during adolescence, exposure to carefully curated online images — which often present an unrealistic ideal — can lead to anxiety and low self-esteem."

Phân tích câu 1: - Although...communicate → Adverb clause (nhượng bộ) - who live in different countries → Relative clause - that excessive use is damaging... → Noun clause

Phân tích câu 2: - Since the brain is still developing... → Adverb clause (lý do) - which often present an unrealistic ideal → Relative clause (non-restrictive, non-essential info)

Lỗi thường gặp

Lỗi 1: Sentence fragment — dùng dependent clause như câu đơn

• ❌ SAI: Although technology has many benefits. (dependent clause đứng một mình)
• ✅ ĐÚNG: Although technology has many benefits, it also poses risks.
• TẠI SAO: Dependent clause BẮT BUỘC có mệnh đề chính đi kèm. Đây là lỗi nghiêm trọng nhất trong IELTS Writing.

Lỗi 2: Dùng sai dấu phẩy với relative clause

• ❌ SAI: The students, who study hard, tend to succeed. (nếu muốn nói về tất cả sinh viên nói chung — restrictive)
• ✅ ĐÚNG: The students who study hard tend to succeed. (restrictive — chỉ những em học chăm)
• ❌ SAI: My brother who lives in Hanoi is a teacher. (nếu chỉ có một người anh — non-restrictive)
• ✅ ĐÚNG: My brother, who lives in Hanoi, is a teacher. (non-restrictive — thêm thông tin về người đã biết)
• TẠI SAO: Dấu phẩy thay đổi nghĩa của relative clause.

Lỗi 3: Dùng "that" trong non-restrictive relative clause

• ❌ SAI: The Eiffel Tower, that was built in 1889, is in Paris.
• ✅ ĐÚNG: The Eiffel Tower, which was built in 1889, is in Paris.
• TẠI SAO: that không dùng trong non-restrictive (non-defining) relative clause.

Lỗi 4: Dùng sai subordinating conjunction

• ❌ SAI: Despite she worked hard, she failed. (despite là preposition, không phải conjunction)
• ✅ ĐÚNG: Although she worked hard, she failed.
• ✅ ĐÚNG: Despite working hard, she failed. (despite + gerund/noun)
• ❌ SAI: Because of the economy is growing... (because of + noun, không phải clause)
• ✅ ĐÚNG: Because the economy is growing... (because + clause)
• ✅ ĐÚNG: Because of economic growth... (because of + noun phrase)
• TẠI SAO: Phân biệt because (conjunction + S + V) vs because of (preposition + noun/gerund); although (conjunction) vs despite/in spite of (preposition).

Lỗi 5: "Although... but..." — dùng hai liên từ đối lập

• ❌ SAI: Although she worked hard, but she failed.
• ✅ ĐÚNG: Although she worked hard, she failed.
• ✅ ĐÚNG: She worked hard, but she failed.
• TẠI SAO: although và but đều diễn đạt tương phản — dùng cả hai là thừa và sai ngữ pháp. Chọn một.

Lỗi 6: Thiếu dấu phẩy khi dependent clause đứng đầu

• ❌ SAI: Although the economy grew inequality remained high.
• ✅ ĐÚNG: Although the economy grew, inequality remained high.
• TẠI SAO: Khi dependent clause đứng trước independent clause, bắt buộc có dấu phẩy ngăn cách.

So sánh với

	Simple	Compound	Complex
Clauses	1 independent	2+ independent	1 independent + 1+ dependent
Liên từ	Không	FANBOYS	Subordinating conj. / relative pronoun
Ví dụ	She works.	She works hard, so she succeeds.	Because she works hard, she succeeds.
Hai vế bình đẳng?	—	Có	Không (dependent phụ thuộc main)
Emphasizes	Một ý	Hai ý bình đẳng	Một ý chính + ý phụ/bổ trợ
IELTS target	Band 5	Band 6	Band 7+

Khi nào dùng compound vs. complex: - Compound (She studied hard, so she passed): Hai ý ngang nhau, bình đẳng về tầm quan trọng - Complex (Because she studied hard, she passed): Một ý chính (kết quả), một ý phụ (lý do); hoặc khi muốn nhấn mạnh mối quan hệ cụ thể (nhượng bộ, điều kiện, thời gian...)

Lưu ý cho người học Việt Nam

Tiếng Việt có cấu trúc tương tự complex sentence — "Vì... nên...", "Mặc dù... nhưng...", "Khi... thì...". Tuy nhiên có hai điểm khác biệt quan trọng:

1. "Although... but..." trong tiếng Anh là SAI: - Tiếng Việt: "Mặc dù cô ấy học chăm, nhưng cô ấy không đỗ." → Tự nhiên hoàn toàn - Tiếng Anh: "Although she studied hard, she didn't pass." → Không có but - Lỗi này rất phổ biến ở người học Việt.

2. Despite vs. Although: - despite / in spite of + noun / gerund - although / though / even though + S + V

Tiếng Việt	Tiếng Anh (đúng)
Mặc dù có nhiều thách thức...	Despite the many challenges... (noun)
Mặc dù có nhiều thách thức...	Although there are many challenges... (clause)
❌ Mặc dù có nhiều thách thức...	Despite there are many challenges... (SAI)

Mẹo: Nếu sau "mặc dù" là chủ ngữ + động từ → dùng although. Nếu là danh từ/cụm danh từ → dùng despite/in spite of.

Ứng dụng trong IELTS

IELTS Speaking — Complex sentences tạo độ phức tạp ngữ pháp

Trong Speaking Part 3, các examiner tìm kiếm: - "I think that access to quality education should be considered a basic human right, which means governments have a responsibility to fund it." - "Although I understand why some people prefer online learning, I personally believe that face-to-face interaction is irreplaceable." - "Since technology is advancing so rapidly, it's difficult to predict what jobs will exist in 20 years."

IELTS Writing Task 2 — Building a Band 7 paragraph

Cấu trúc một luận điểm Band 7: 1. Topic sentence (có thể simple hoặc compound) 2. Explanation (complex sentence với because/since/as) 3. Concession (complex sentence với although/while/even though) 4. Example + elaboration (relative clause để thêm chi tiết)

Ví dụ:

"(1) Remote work has fundamentally altered the modern workplace. (2) Since employees no longer need to commute, they gain additional hours that can be used for personal development or family time. (3) While some workers thrive in home environments, others struggle with the isolation that remote work can create. (4) Countries where flexible work arrangements were common before the pandemic, such as the Netherlands, have reported higher levels of employee satisfaction than those where rigid office cultures persist."

Combining short sentences (cách thực hành)

From simple to complex (worked examples)

PHẦN 1: BẮT ĐẦU — CÂU ĐƠN

Câu đơn có một chủ ngữ và một động từ:

[Subject] + [Verb] + [Object/Complement].

• "Technology is useful."
• "Cities are growing."
• "Students use social media."
• "Exercise reduces stress."

Không sai, nhưng quá đơn giản. Hãy nâng cấp từng bước.

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PHẦN 2: BƯỚC 1 — THÊM LÝ DO

[Simple sentence] because / since / as [reason].

Transformation:

Câu đơn	+ Lý do
"Technology is useful."	"Technology is useful because it allows people to access information instantly."
"Cities are growing."	"Cities are growing as more people migrate from rural areas in search of better opportunities."
"Exercise reduces stress."	"Exercise reduces stress since it triggers the release of endorphins in the brain."

"Because" = lý do cụ thể, trực tiếp "Since" / "As" = lý do được xem là đã biết (slightly softer, academic)

Lưu ý: "Because" mạnh nhất trong ba từ — dùng khi lý do là trọng tâm của ý bạn muốn nói.

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PHẦN 3: BƯỚC 2 — THÊM KẾT QUẢ

[Simple sentence], so [result].
[Simple sentence]. Therefore, / As a result, / Consequently, [result].
[Simple sentence], which means (that) [result].

Transformation:

Câu đơn + lý do	+ Kết quả
"Technology allows instant access to information."	"...so people can now learn almost anything without leaving home."
"More people are moving to cities."	"...which means that urban infrastructure is under increasing strain."
"Exercise releases endorphins."	"As a result, regular physical activity can significantly improve mental wellbeing."

Before/after (đầy đủ):

• Before: "Exercise is good. It makes you feel better."
• After: "Regular exercise releases endorphins, which means that it can significantly improve mood and reduce feelings of anxiety — particularly for individuals under chronic stress."

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PHẦN 4: BƯỚC 3 — THÊM TƯƠNG PHẢN

[Main point], but [contrast].
Although [contrast], [main point].
While [side A], [side B].
[Main point]. However, [contrast].

Transformation:

Câu không có tương phản	+ Tương phản
"Technology is useful."	"Technology is useful, but it can also be a source of distraction and dependency."
"Cities offer opportunities."	"While cities offer greater career opportunities, they also come with higher living costs and significant social pressures."
"Social media connects people."	"Social media can connect people across vast distances. However, it has also been linked to rising rates of loneliness and anxiety, particularly among teenagers."

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PHẦN 5: BƯỚC 4 — THÊM RELATIVE CLAUSE

[Noun] + which/that [adds information about noun].
[Noun] + who [adds information about a person].
[Place] + where [adds information about location].
[Time] + when [adds information about a time].

Relative clause giúp bổ sung thông tin về danh từ ngay bên trong câu — không cần tách ra thành câu mới.

Transformation:

Câu không có relative clause	+ Relative clause
"Social media is popular."	"Social media, which has transformed how billions of people communicate, is now a dominant force in public discourse."
"Cities attract young people."	"Cities attract young people who are looking for career opportunities and a more dynamic social environment."
"The pandemic changed work culture."	"The pandemic, which forced millions to work from home, fundamentally altered expectations around workplace flexibility."

Thêm relative clause để thay thế câu thứ hai:

• Before: "Many countries face housing shortages. This creates social inequality."
• After: "Many countries face housing shortages, which contribute directly to rising social inequality and reduced social mobility."

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PHẦN 6: BƯỚC 5 — THÊM ĐIỀU KIỆN

[Main clause] if / unless / as long as / provided that [condition].
If [condition], [main clause].

Điều kiện thêm sắc thái và tính chính xác vào lập luận.

Transformation:

Câu không có điều kiện	+ Điều kiện
"Technology improves productivity."	"Technology can improve productivity significantly, provided that employees receive adequate training and the right tools."
"Remote work is beneficial."	"Remote work can be highly beneficial, as long as clear communication structures are maintained."
"Stricter laws will reduce crime."	"Stricter laws may reduce certain forms of crime, if they are enforced consistently and fairly."

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PHẦN 7: KẾT HỢP — CÂU PHỨC HOÀN CHỈNH

Bây giờ, kết hợp nhiều bước để tạo ra một câu phức thực sự có chiều sâu.

Transformation hoàn chỉnh — Example 1:

Câu đơn gốc: "Technology changes work."

Bước 1 (+reason): "Technology changes work because it automates many routine tasks."

Bước 2 (+result): "Technology automates many routine tasks, which means that workers must continually update their skills."

Bước 3 (+contrast): "While technology automates many routine tasks, which reduces labour costs for companies, it also demands that workers continually invest in upskilling."

Bước 4 (+condition): "While technology undoubtedly automates many routine tasks, reducing costs for businesses, its overall impact on employment is likely to be positive, provided that governments invest adequately in retraining programmes."

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Transformation hoàn chỉnh — Example 2:

Câu đơn gốc: "Cities are noisy."

+Lý do: "Cities are noisy because of the constant flow of traffic and large concentrations of people."

+Kết quả: "...noise pollution, which can disrupt sleep and contribute to chronic stress."

+Tương phản: "While urban environments are inevitably noisier than rural areas, which some residents find deeply disruptive, others argue that the energy and vibrancy of city life more than compensates for the drawback of noise."

+Điều kiện: "While urban noise levels are unlikely to decrease significantly in the near future, their health impacts can be mitigated if city planners prioritise green spaces, noise barriers, and pedestrianised zones in urban design."

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Transformation hoàn chỉnh — Example 3 (Speaking answer):

Q: "Do you think social media is good for society?"

Band 5 answer: "I think social media is good. It helps people communicate. But it also has problems."

Band 7 answer: "I think social media has real benefits, particularly in terms of enabling people to stay connected with friends and family across long distances. However, platforms that prioritise engagement over accuracy have also contributed to the spread of misinformation — which is a problem that governments and tech companies are increasingly struggling to address. On balance, I'd say the benefits outweigh the drawbacks, as long as users develop critical media literacy skills."

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PHẦN 8: CHECKLIST — Câu của bạn đã đủ phức chưa?

Yếu tố	Câu có chưa?
Ít nhất 1 mệnh đề phụ	□
Lý do hoặc kết quả được giải thích	□
Tương phản hoặc sắc thái được nêu	□
Relative clause hoặc participle phrase	□
Điều kiện hoặc nhượng bộ (nếu phù hợp)	□

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Lỗi thường gặp

Lỗi 1: Câu quá dài và mất mạch

Câu phức không phải là câu dài vô tội vạ. Nếu một câu có hơn 3-4 mệnh đề phụ, hãy tách ra.

• ❌ "Technology is useful because it helps people communicate, which means they can work remotely, which reduces costs, which is why companies prefer it."
• ✅ Chia thành 2 câu: "Technology enables remote communication, significantly reducing operational costs for businesses. As a result, it has become an increasingly attractive option for employers worldwide."

Lỗi 2: Thêm relative clause nhưng sai đại từ

• ❌ "The policy which it was introduced last year..."
• ✅ "The policy which was introduced last year..." / "The policy that was introduced last year..."

Lỗi 3: Quá nhiều "because" trong một đoạn

• Đa dạng hóa: because → since → as → given that → due to the fact that

Lỗi 4: "Although" + "but" trong cùng một câu

• ❌ "Although technology is useful, but it has drawbacks."
• ✅ "Although technology is useful, it has drawbacks." / "Technology is useful, but it has drawbacks."

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Bài tập luyện

Nâng cấp các câu đơn sau qua từng bước:

1. "Exercise is important." → Thêm lý do → Thêm kết quả
2. "Young people use social media." → Thêm relative clause → Thêm tương phản
3. "Governments should act." → Thêm điều kiện → Thêm nhượng bộ

Đáp án gợi ý:

1. "Exercise is important because it improves both physical and mental health. As a result, incorporating regular activity into daily routines has been shown to reduce the risk of numerous chronic diseases."

2. "Young people who have grown up with social media tend to use it as their primary source of news and social interaction. However, there are growing concerns about its impact on attention spans and the quality of real-world relationships."

3. "Governments should act decisively to address climate change, provided that such action is coordinated internationally and does not unfairly burden developing economies. While the short-term economic costs may be significant, the long-term consequences of inaction would be far more severe."

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Tóm tắt nhanh

TỪNG BƯỚC NÂNG CẤP CÂU:

BƯỚC 1 — +LÝ DO:
  "Technology is useful because it saves time."
  "...since / as [reason]"

BƯỚC 2 — +KẾT QUẢ:
  "...so people learn faster."
  "..., which means that / therefore / as a result, ..."

BƯỚC 3 — +TƯƠNG PHẢN:
  "..., but / although / while / however, ..."

BƯỚC 4 — +RELATIVE CLAUSE:
  "Social media, which connects billions of people, ..."
  "...a problem that governments must address."

BƯỚC 5 — +ĐIỀU KIỆN:
  "...provided that / if / as long as / unless ..."

KẾT HỢP:
  "While [A — contrast], [B — main point],
  which [result], provided that [condition]."

MỤC TIÊU: Câu CHÍNH XÁC và CÓ CHIỀU SÂU — không phải câu DÀI.

PHẦN 1: AND / BUT — Nối thêm thông tin hoặc tương phản

[Sentence A] + and/but + [Sentence B without repeated subject]

Before → After với "and":

❌ Trước	✅ Sau
"I study English. I also practice speaking."	"I study English and practice speaking regularly."
"She is kind. She is hardworking."	"She is kind and hardworking."
"He moved to the city. He found a job there."	"He moved to the city and found a job there."

Before → After với "but":

❌ Trước	✅ Sau
"The city is exciting. It is expensive."	"The city is exciting but expensive."
"I like coffee. I don't drink it at night."	"I like coffee but don't drink it at night."
"The plan was good. It didn't work."	"The plan was good but didn't work out."

Tránh lặp chủ ngữ khi dùng "and/but":

• ❌ "She studied hard. She passed the exam."
• ✅ "She studied hard and passed the exam." (bỏ "she" thứ hai vì cùng chủ ngữ)

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PHẦN 2: BECAUSE / SINCE / AS — Nối lý do

[Main idea] because/since/as [reason].
Because/Since/As [reason], [main idea].

Before → After với "because":

❌ Trước	✅ Sau
"I take the bus. My office is far away."	"I take the bus because my office is quite far from home."
"She was nervous. It was her first interview."	"She was nervous because it was her first interview."
"He started exercising. He wanted to feel healthier."	"He started exercising because he wanted to feel healthier."

"Since" và "as" — thay thế "because" (trang trọng hơn một chút):

• "Since public transport is unreliable, most people prefer to drive."
• "As the weather was so beautiful, we decided to walk instead."
• "Since she had lived there for ten years, she knew the city very well."

Lưu ý: "Since" cũng có nghĩa thời gian ("since 2010"). Ngữ cảnh thường làm rõ. Nếu muốn chắc chắn, dùng "because".

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PHẦN 3: WHO / WHICH / THAT — Relative Clauses

[Noun] + who/which/that + [additional information about that noun]

Relative clauses cho phép bạn thêm thông tin về một người hoặc vật ngay trong câu, thay vì tách thành câu riêng.

Before → After với "who":

❌ Trước	✅ Sau
"I have a teacher. She inspires me a lot."	"I have a teacher who inspires me a lot."
"My friend lives in London. He works in finance."	"My friend, who lives in London, works in finance."

Before → After với "which":

❌ Trước	✅ Sau
"I read a book. It changed my perspective."	"I read a book that changed my perspective."
"The city has great public transport. It makes commuting easy."	"The city has great public transport, which makes commuting easy."

Before → After với "that":

• "I found an app that helps me practice vocabulary every day."
• "She chose a career that she is genuinely passionate about."
• "This is the kind of problem that requires a long-term solution."

Mẹo: Dùng "who" cho người, "which" cho vật (non-defining), "that" cho người hoặc vật (defining — không có dấu phẩy).

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PHẦN 4: V-ING PHRASE — Nối hành động đồng thời hoặc nguyên nhân

[Main clause], + V-ing [additional action / reason].
V-ing [reason/context], [main clause].

Đây là cấu trúc nâng cao hơn nhưng rất tự nhiên và hiệu quả:

Before → After:

❌ Trước	✅ Sau
"I walk to work. I listen to podcasts at the same time."	"I walk to work, listening to podcasts along the way."
"She sat by the window. She was reading a book."	"She sat by the window, reading a book."
"He grew up in a small town. He learned to appreciate nature."	"Growing up in a small town, he learned to appreciate nature."
"I was tired. I still finished the report."	"Feeling tired, I still managed to finish the report."

Chú ý: Chủ ngữ của V-ing phrase phải là chủ ngữ của mệnh đề chính. Nếu khác, câu sẽ sai (dangling modifier): - ❌ "Walking home, the rain started." (mưa không thể "walking home") - ✅ "Walking home, I got caught in the rain."

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PHẦN 5: WHERE / WHEN — Thêm bối cảnh địa điểm hoặc thời gian

[Noun] + where [location information]
[Noun/Time] + when [time/circumstance information]

Before → After:

❌ Trước	✅ Sau
"I grew up in Hanoi. There were few tall buildings then."	"I grew up in Hanoi, where there were few tall buildings at the time."
"I remember a day. My father took me to the sea."	"I remember a day when my father took me to the sea for the first time."
"There's a café near my office. I go there every morning."	"There's a café near my office where I go every morning."

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PHẦN 6: BEFORE / AFTER / WHILE / WHEN — Nối sự kiện theo thứ tự thời gian

Before/After/When + [Sentence], [Main sentence].
[Main sentence] before/after/when + [Sentence].

Before → After:

❌ Trước	✅ Sau
"I finished work. Then I went to the gym."	"After finishing work, I went to the gym." / "I went to the gym after finishing work."
"I was a student. I lived in a dormitory."	"When I was a student, I lived in a dormitory."
"She arrived home. Then she made dinner."	"As soon as she arrived home, she made dinner."

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Áp dụng vào IELTS Speaking

Part 2 — Kể về trải nghiệm (before/after rõ ràng):

❌ Rời rạc:

"I visited Hội An. It was beautiful. There were many old buildings. I liked the lanterns. I took many photos."

✅ Câu kết hợp tự nhiên:

"I visited Hội An last year, which is a small ancient town in central Vietnam that is famous for its colourful lanterns and well-preserved architecture. I was genuinely amazed by the old buildings lining the riverside, where I spent most of the afternoon taking photos and exploring the local streets."

Part 3 — Phân tích có chiều sâu:

❌ Rời rạc:

"People use phones a lot. It is a problem. They don't talk to each other."

✅ Câu kết hợp:

"People use their phones so frequently that they often fail to engage with those around them, which is particularly noticeable in public spaces where people sit together without making any real conversation."

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Lỗi thường gặp

Lỗi 1: Dùng "which" khi nên dùng "who"

• ❌ "She is a teacher which works at my school."
• ✅ "She is a teacher who works at my school."

Lỗi 2: Nối quá nhiều ý với "and...and...and"

• ❌ "I went to the market and bought vegetables and came home and cooked dinner and watched TV."
• ✅ "I went to the market to buy vegetables, then came home to cook dinner before settling in for the evening."

Lỗi 3: V-ing phrase với sai chủ ngữ

• ❌ "Walking to school, the weather suddenly changed."
• ✅ "Walking to school, I noticed the weather suddenly change."

Lỗi 4: Lặp chủ ngữ khi không cần

• ❌ "She studied hard and she passed the exam."
• ✅ "She studied hard and passed the exam."

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Bài tập luyện

Nối hai câu thành một câu tự nhiên hơn:

1. "I have a sister. She lives in Australia." → ___
2. "I enjoy cooking. It helps me relax." → ___
3. "The film was long. It was very entertaining." → ___
4. "He moved to the city. He found a better job." → ___
5. "I remember a holiday. We went to the beach." → ___

Viết lại đoạn sau, kết hợp câu ngắn:

1. "I wake up early. I exercise. I feel better. I can focus at work."

Đáp án gợi ý

1. "I have a sister who lives in Australia."
2. "I enjoy cooking because it helps me relax." / "I enjoy cooking, which I find really relaxing."
3. "The film was long but very entertaining." / "Although it was long, the film was very entertaining."
4. "He moved to the city and found a better job." / "He moved to the city, where he found a better job."
5. "I remember a holiday when we went to the beach."
6. "I wake up early to exercise, which helps me feel better and focus more effectively at work." / "By waking up early and exercising, I find I can concentrate much better throughout the working day."

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Tóm tắt nhanh

AND / BUT → thêm thông tin hoặc tương phản (cùng chủ ngữ: bỏ "she/he/it" thứ hai):
  She studied and passed. | The city is exciting but expensive.

BECAUSE / SINCE / AS → giải thích lý do:
  I take the bus because my office is far away.

WHO / WHICH / THAT → thêm thông tin về người/vật:
  a teacher who inspires me | a book that changed my life
  great transport, which makes commuting easy

V-ING PHRASE → hành động đồng thời hoặc lý do:
  Walking to work, I listen to podcasts.
  Growing up in the countryside, she learned to love nature.
  → Chủ ngữ V-ing PHẢI là chủ ngữ của mệnh đề chính

WHERE / WHEN → bối cảnh địa điểm/thời gian:
  a café where I go every morning
  a day when everything changed

BEFORE / AFTER / WHILE:
  After finishing work, I went to the gym.
  When I was a student, I lived in a dormitory.

Bài tập luyện

Nối bằng cách phù hợp

1. "She failed the exam." + "She studied very hard." (nhượng bộ — although)
2. "The city lacks clean water." + "The government must invest in infrastructure." (kết quả — therefore)
3. "He is the researcher." + "His work changed our understanding of climate change." (relative clause — whose)
4. "Technology creates jobs." + "It eliminates many traditional ones." (tương phản — while)
5. "We act now." + "The effects will be irreversible." (điều kiện — unless)

Sửa lỗi

1. "Although she worked hard, but she didn't succeed."
2. "Despite she was tired, she continued working."
3. "The researchers, that discovered the vaccine, received a Nobel Prize."
4. "Because of the economy is growing, more jobs are available."
5. "When he arrived at the station. The train had already left."

Đáp án

Nối câu: 1. Although she studied very hard, she failed the exam. 2. The city lacks clean water; therefore, the government must invest in infrastructure. 3. He is the researcher whose work changed our understanding of climate change. 4. While technology creates jobs, it also eliminates many traditional ones. 5. Unless we act now, the effects will be irreversible.

Sửa lỗi: 1. → Although she worked hard, she didn't succeed. (bỏ but — không dùng although + but cùng lúc) 2. → Although she was tired, she continued working. (despite + noun/gerund; although + clause) 3. → The researchers who discovered the vaccine received a Nobel Prize. (non-restrictive: The researchers, who discovered...; restrictive: không dấu phẩy — that có thể dùng nếu restrictive) 4. → Because the economy is growing, more jobs are available. (because of + noun; because + S + V) 5. → When he arrived at the station, the train had already left. (dependent clause không đứng một mình)

Tóm tắt nhanh

1. Complex sentence = 1 independent clause + 1+ dependent clause
2. Ba loại dependent clause: adverb clause (because, although, if, when...), relative clause (who, which, that), noun clause (that, what, whether)
3. Dependent clause đứng đầu câu → dấu phẩy sau nó
4. Relative clause restrictive (xác định) → không dấu phẩy; non-restrictive (thêm thông tin) → có dấu phẩy
5. Lỗi phổ biến: although...but (chọn một), despite + clause (sai — dùng despite + noun/gerund), dependent clause đứng một mình
6. Complex sentences là yêu cầu bắt buộc cho IELTS Band 7+ (Grammatical Range & Accuracy)