Tóm tắt

To-infinitive = to + động từ nguyên thể — được dùng sau một số động từ nhất định, để diễn tả mục đích, và sau nhiều tính từ; khác với gerund (V-ing) ở chỗ nó hướng về hành động sẽ xảy ra hoặc kết quả mong muốn.

Tại sao quan trọng

To-infinitive có mặt trong hầu hết mọi câu tiếng Anh phức tạp: - Sau động từ phổ biến: want to go, hope to find, decide to stay - Diễn tả mục đích: I study English to get a better job. - Sau tính từ: It's important to practise every day.

Trong IELTS Speaking và Writing, bạn cần to-infinitive để: - Nói về mong muốn, kế hoạch, quyết định (Part 1, 2, 3) - Giải thích lý do, mục đích trong bài luận (Writing Task 2) - Tránh lỗi nhầm với gerund — một trong những lỗi thường gặp nhất ở Band 5-6

Định nghĩa

To-infinitive = to + base verb (động từ ở dạng nguyên thể)

To-infinitive Nghĩa
to go đi
to learn học
to speak nói
to finish hoàn thành
to be là / tồn tại
to have có

Phân biệt "to" giới từ và "to" infinitive: - "I walk to school." → to = giới từ (chỉ hướng) - "I want to go to school." → to go = to-infinitive (sau want)

Cấu trúc

to + base verb (không thay đổi theo chủ ngữ hay thời)

Phủ định to-infinitive:

not + to + base verb
  • She decided not to come to the party.
  • I chose not to say anything.

To-infinitive bị động:

to + be + past participle
  • The problem needs to be solved immediately.
  • She wants to be promoted this year.

To-infinitive hoàn thành:

to + have + past participle
  • She claims to have met him before.
  • I'm lucky to have had such a great teacher.

Cách dùng phổ biến

1. To-infinitive sau động từ (Verb + to-infinitive)

Đây là cách dùng phổ biến nhất. Các động từ dưới đây bắt buộc đi với to-infinitive, không dùng gerund:

Verb + to + base verb
Động từ Ví dụ
want I want to travel the world.
hope She hopes to find a new job.
plan We plan to move next year.
decide He decided to stay home.
need You need to practise more.
expect I expect to finish by noon.
promise She promised to help me.
agree They agreed to work together.
refuse He refused to apologise.
offer She offered to drive us there.
manage I managed to fix the problem.
fail He failed to meet the deadline.
tend People tend to forget names.
afford We can't afford to waste time.
appear She appears to be very busy.
seem It seems to be getting colder.
  • ❌ SAI: I want going abroad.
  • ✅ ĐÚNG: I want to go abroad.

2. To-infinitive diễn tả mục đích (Purpose)

Dùng to-infinitive thay cho "in order to" — ngắn gọn hơn, tự nhiên hơn:

[main clause] + to + base verb (= in order to + base verb)
  • I study every day to improve my English.
  • She went to the library to find information for her essay.
  • We need to act now to protect the environment.
  • Many people move to cities to find better opportunities.

Khi câu cần trang trọng hơn, dùng "in order to": - Governments must invest in education in order to reduce inequality.

Lưu ý: Không dùng "for + to-infinitive" để diễn tả mục đích khi chủ ngữ không thay đổi. - ❌ SAI: I study for to improve my English. - ✅ ĐÚNG: I study to improve my English.

3. To-infinitive sau tính từ (Adjective + to-infinitive)

It + be + adjective + to + base verb
Subject + be + adjective + to + base verb

Cấu trúc "It is + adj + to-inf": - It's important to practise speaking every day. - It's difficult to master a new language. - It was surprising to hear the news. - It is essential to consider all perspectives.

Sau tính từ mô tả cảm xúc hoặc thái độ: - I'm happy to help you. - She was surprised to see me there. - He was reluctant to admit his mistake. - I'm ready to start.

Sau tính từ mô tả thứ tự/mức độ (too/enough): - She's old enough to make her own decisions. - The problem is too complex to ignore. - He spoke too quickly to understand.

4. To-infinitive sau danh từ (Noun + to-infinitive)

Dùng to-infinitive để mô tả chức năng hoặc ý định liên quan đến danh từ:

Noun + to + base verb
  • I have a lot of work to do today.
  • She is looking for a place to live.
  • He has the ability to learn quickly.
  • This is an opportunity to improve your skills.
  • Is there anything to eat in the fridge?

5. To-infinitive sau "wh-words" (Question Word + to-infinitive)

Dùng sau how, what, where, when, who, which để rút gọn mệnh đề phụ:

wh-word + to + base verb
  • I don't know what to say.
  • She wasn't sure where to go.
  • Could you tell me how to get there?
  • I've been wondering whether to apply for the job.
  • We need to decide when to start.

Dấu hiệu nhận biết

Dùng to-infinitive khi... Ví dụ
Sau: want, hope, plan, decide, need, agree, refuse, offer, manage I want to learn.
Diễn tả mục đích (= để làm gì) I came here to study.
Sau: It is + adj + ... It is hard to explain.
Sau: too + adj / adj + enough Too tired to continue
Sau: wh-word (how, what, where...) I know how to do it.
Sau: first, last, next, only + noun She was the first to arrive.

Ví dụ

Ví dụ giao tiếp tự nhiên

  • A: Why are you studying so hard?

  • B: I want to pass my IELTS exam and to apply for a scholarship abroad.

  • A: What are your plans for the future?

  • B: I hope to start my own business one day. I've decided to save money first so that I can afford to take that risk.

Ví dụ IELTS

(Speaking Part 1) "I tend to read in my free time. I find it difficult to concentrate if there's too much noise around me, so I prefer to read in quiet places."

(Speaking Part 2) "I'd like to talk about a goal I've been working towards. I decided to learn coding two years ago, not just to improve my career prospects, but also to challenge myself."

(Writing Task 2) "Governments need to invest in public transport to reduce traffic congestion. It is also essential to encourage citizens to consider more sustainable options. Failing to address this issue now will have long-term consequences."

Lỗi thường gặp

Lỗi 1: Dùng gerund thay to-infinitive sau want/hope/plan/decide

  • ❌ SAI: I want going abroad.
  • ✅ ĐÚNG: I want to go abroad.
  • ❌ SAI: She hopes finding a better job.
  • ✅ ĐÚNG: She hopes to find a better job.
  • ❌ SAI: We plan moving to a new city.
  • ✅ ĐÚNG: We plan to move to a new city.
  • TẠI SAO: Trong tiếng Việt, "muốn đi", "hy vọng tìm", "dự định chuyển" đều dùng động từ trực tiếp. Trong tiếng Anh, nhóm want/hope/plan/decide chỉ đi với to-infinitive.

Lỗi 2: Bỏ "to" trong to-infinitive

  • ❌ SAI: I decided stay home.
  • ✅ ĐÚNG: I decided to stay home.
  • ❌ SAI: She managed finish the project.
  • ✅ ĐÚNG: She managed to finish the project.
  • TẠI SAO: To-infinitive trong tiếng Anh bắt buộc phải có "to" (trừ trường hợp bare infinitive sau modal verbs).

Lỗi 3: Dùng to-infinitive sau giới từ (phải dùng gerund)

  • ❌ SAI: I'm interested in to learn more.
  • ✅ ĐÚNG: I'm interested in learning more.
  • ❌ SAI: She left without to say anything.
  • ✅ ĐÚNG: She left without saying anything.
  • TẠI SAO: Sau giới từ (in, on, of, for, without, about...) luôn dùng gerund, không bao giờ dùng to-infinitive.

Lỗi 4: Dùng "for to" thay vì chỉ "to" cho mục đích

  • ❌ SAI: I study English for to get a better job.
  • ✅ ĐÚNG: I study English to get a better job.
  • TẠI SAO: "For to + verb" không phải cấu trúc tiếng Anh chuẩn. Chỉ dùng "to" hoặc "in order to".

Lỗi 5: Nhầm "to" giới từ với "to" of to-infinitive

  • "I'm looking forward to meeting you." → to = giới từ → sau đó dùng gerund
  • "I want to meet you." → to = dấu hiệu of infinitive → sau đó dùng base verb
  • TẠI SAO: "look forward to", "be used to", "in addition to" đều có "to" là giới từ → dùng gerund sau đó.

So sánh với

To-Infinitive vs. Gerund

To-infinitive Gerund
Hình thức to + base verb base verb + -ing
Hướng về Tương lai / kết quả mong muốn Hành động chung chung / đã xảy ra
Sau động từ want, hope, plan, decide, need, agree... enjoy, avoid, mind, finish, keep, suggest...
Sau giới từ ❌ Không dùng ✅ Luôn dùng
Làm chủ ngữ To swim is fun. (ít tự nhiên) Swimming is fun. (tự nhiên hơn)

Động từ dùng được cả hai nhưng đổi nghĩa:

Động từ + Gerund + To-infinitive
stop He stopped smoking. (bỏ thuốc) He stopped to smoke. (dừng lại để hút)
remember I remember meeting her. (nhớ đã gặp) Remember to call him. (nhớ gọi nhé)
forget I'll never forget seeing that film. (quên lần đã xem) Don't forget to buy milk. (đừng quên mua)
try Try adding more spice. (thử thêm gia vị xem) Try to sleep early. (cố gắng ngủ sớm)
regret I regret saying that. (hối tiếc đã nói) I regret to inform you... (tiếc phải thông báo)

Lưu ý cho người học Việt Nam

Tiếng Việt không có sự phân biệt này — "tôi muốn đi", "tôi thích đi" đều dùng động từ trực tiếp. Trong tiếng Anh: - "I want to go" (want → to-infinitive) - "I enjoy going" (enjoy → gerund)

Mẹo nhớ nhanh: 1. want, hope, plan, decide, need, agree, refuse, manage, offer, promise → to-infinitive 2. enjoy, avoid, mind, finish, keep, suggest, consider, miss, practise → gerund 3. Sau giới từ → gerund (luôn luôn) 4. Mục đích (để làm gì) → to-infinitive 5. It is + adj + ??? → to-infinitive

Ứng dụng trong IELTS

IELTS Speaking — Mẫu câu hữu ích

Nói về mục tiêu / kế hoạch: - "I'm planning to apply for a master's degree abroad." - "My goal is to become fluent in English within two years." - "I've always wanted to travel to South America."

Giải thích lý do / mục đích: - "I started exercising to improve my health." - "I moved to the city to find better career opportunities." - "People use social media to stay connected with friends."

Nói về ý kiến: - "It's important to consider both sides of the argument." - "It would be difficult to solve this problem without government support." - "I think it's essential to maintain a healthy work-life balance."

IELTS Writing — To-infinitive cho câu học thuật

Diễn tả mục đích: - "Governments must act now to prevent further environmental damage." - "Stricter laws are needed to discourage dangerous behaviour."

Diễn tả sự cần thiết: - "It is crucial to address the root causes of poverty." - "It remains important to consider the long-term consequences."

Diễn tả khả năng / xu hướng: - "Young people tend to prefer digital communication." - "This approach appears to be more effective than previous methods."

Bài tập luyện

Điền đúng dạng: To-infinitive hay Gerund?

  1. I hope _____ (travel) to Europe next summer.
  2. She enjoys _____ (cook) for her family.
  3. He decided _____ (study) medicine.
  4. They finished _____ (write) the report.
  5. I go to the gym _____ (stay) healthy.
  6. It's difficult _____ (learn) a new language in a short time.
  7. She managed _____ (solve) the problem on her own.
  8. I look forward to _____ (see) you soon.

Sửa lỗi

  1. I want going to the cinema tonight.
  2. She's very good at to speak English.
  3. It's important practise every day.
  4. I study English for to get a better job.
  5. We plan moving to a larger apartment.

Đáp án

Điền đúng dạng: 1. to travel (sau hope → to-infinitive) 2. cooking (sau enjoys → gerund) 3. to study (sau decided → to-infinitive) 4. writing (sau finished → gerund) 5. to stay (mục đích → to-infinitive) 6. to learn (It's + adj + to-inf) 7. to solve (sau managed → to-infinitive) 8. seeing (look forward to → to = giới từ → gerund)

Sửa lỗi: 1. I want to go to the cinema. 2. She's very good at speaking English. 3. It's important to practise every day. 4. I study English to get a better job. 5. We plan to move to a larger apartment.

Tóm tắt nhanh

  1. To-infinitive = to + động từ nguyên thể: to go, to learn, to speak
  2. Sau want, hope, plan, decide, need, agree, refuse, manage, offer, promise → to-infinitive
  3. Diễn tả mục đích (để làm gì): I study to improve my English
  4. Sau It is + adjective: It's important to practise
  5. Sau tính từ + enough / too + tính từ: old enough to decide, too hard to ignore
  6. Phủ định: not to + verb → She decided not to come
  7. Sau giới từ → KHÔNG dùng to-infinitive, dùng gerund thay thế