Vietnamese có thể + predicate presents something as possible: circumstances allow it, a person has the capacity to do it, or the speaker considers it one possible truth. English often uses can, could, or may for the same territory, but those words also express permission, requests, and habits. Do not assume that every English can should become có thể.
The unifying idea is an open path rather than authorization. Mai tôi có thể đến can mean that coming is feasible or that the speaker may in fact come. It does not normally announce that an authority has granted permission. Learned skills with biết and permission or opportunity with được have their own pages.
Form and the core meanings
The neutral order is subject + có thể + predicate. Có thể does not change for person or tense.
Tôi có thể đến sớm hơn nếu cuộc họp kết thúc đúng giờ.
I can come earlier if the meeting ends on time.
Here circumstances determine whether coming is feasible. With a human subject, context may instead foreground physical, mental, or practical capacity:
Sau vài tuần vật lý trị liệu, bà đã có thể tự đi lại trong nhà.
After a few weeks of physiotherapy, she was able to walk around the house by herself.
With a whole proposition, có thể often means “possibly” or “may”:
Chiều nay có thể mưa, nên anh mang áo mưa đi nhé.
It may rain this afternoon, so take a raincoat with you.
These uses overlap because all of them deny inevitability or impossibility. They differ in what supplies the possibility: a person's capacity, external circumstances, or the speaker's assessment of evidence.
A decision aid within the modal system
Vietnamese modality is distributed across verbs, adverbs, particles, and clause frames. The following expressions are therefore alternatives in meaning, not conjugated forms of one modal verb.
| Form | Core question | Minimal contrast |
|---|---|---|
| phải | Is it required? | phải đi — must go |
| cần | Is it needed for a purpose? | cần làm — need to do |
| có thể | Is it possible or within someone's capacity? | có thể đến — can/may come |
| được phép | Has an authority explicitly authorized it? | được phép vào — be permitted to enter |
| nên | Is it advisable? | nên nghỉ — should rest |
| chắc là | Does the speaker consider it probably true? | chắc là đúng — is probably right |
Hôm nay tôi có thể nghỉ ngơi, nhưng ngày mai tôi phải đi làm và cần nộp báo cáo.
Today I can rest, but tomorrow I must go to work and need to submit the report.
This sentence contrasts present feasibility with obligation and goal-oriented need. It does not say whether a manager has authorized the day off. To make permission explicit, say Tôi được nghỉ hôm nay or Tôi được phép nghỉ hôm nay.
Capacity is not the same as learned skill
Có thể is natural when present circumstances or general capability are at issue.
Tôi có thể đọc tài liệu này nếu anh cho tôi thêm một ngày.
I can read this document if you give me one more day.
The speaker knows how to read; time is the obstacle. By contrast, Tôi biết đọc chữ Hán means “I know how to read Chinese characters,” a learned competence. The dedicated Biết plus Verb page develops this contrast.
For a temporary physical condition, có thể is again appropriate:
Tay còn đau nên hôm nay tôi không thể lái xe.
My arm still hurts, so I cannot drive today.
Saying không biết lái xe would instead mean that the person has never learned to drive.
Possibility, probability, and evidence
Epistemic có thể leaves a possibility open; it usually commits the speaker less strongly than chắc “probably/certainly” or hẳn “surely, by inference.” Có lẽ commonly gives a tentative judgment, while dường như reports how the evidence appears.
Dường như Lan chưa đọc tin nhắn; có lẽ cô ấy đang họp.
It seems Lan has not read the message; perhaps she is in a meeting.
Lan có thể đang họp, nhưng Minh hẳn đã đến nơi rồi.
Lan may be in a meeting, but Minh must have arrived by now.
Đèn vẫn sáng nên anh ấy chắc là còn ở văn phòng.
The light is still on, so he is probably still at the office.
There is no perfectly fixed numerical scale. Có thể identifies a live possibility; có lẽ offers a tentative conclusion; chắc là signals stronger confidence; hẳn often presents a confident inference; dường như foregrounds appearance. Evidence, intonation, and context still matter.
Negation, questions, and scope
Không thể + predicate means that the event is impossible or beyond someone's capacity. Có thể không + predicate means that not doing it is possible, or in a question can make a request. Word order changes scope.
Ngày mai tôi không thể đến.
I cannot come tomorrow.
Ngày mai tôi có thể không đến.
I may not come tomorrow.
In the first, negation has scope over possibility: coming is not possible. In the second, possibility has scope over a negative proposition: not coming is one possible outcome.
Anh có thể nói chậm hơn một chút được không?
Could you speak a little more slowly?
This polite request contains có thể and the question frame được không. A literal analysis about ability is possible, but the social act is a request. In a context where the listener's ability is genuinely in doubt, Anh có thể nâng hộp này không? can instead ask whether they are physically able to lift the box.
Time and aspect around có thể
Time and viewpoint markers keep their ordinary positions and meanings. Có thể đã + verb assesses a completed event as possible; có thể đang + verb assesses an ongoing event; sẽ có thể + verb predicts future ability or feasibility. Đã có thể + verb often implies that an earlier obstacle has been overcome.
Họ có thể đã gửi hóa đơn vào tuần trước.
They may have sent the invoice last week.
Tháng sau hệ thống sẽ có thể xử lý nhiều yêu cầu hơn.
Next month the system will be able to process more requests.
Sau khi cập nhật phần mềm, tôi đã có thể mở tệp đó.
After updating the software, I was able to open that file.
Do not insert aspect markers mechanically. Đã có thể mở focuses on acquired or realized ability; it does not necessarily assert that the file was actually opened unless context supplies that conclusion.
A dialogue where one modal changes the interpretation
Mai: Chiều nay anh có thể đến buổi hướng dẫn không?
Nam: Tôi có thể đến lúc bốn giờ, nhưng tôi được vào phòng thí nghiệm chứ?
Mai: Anh được phép vào nếu đã hoàn thành khóa an toàn. Nếu chưa thì anh nên học trực tuyến.
Nam: Tôi học xong rồi. Vậy chắc là không có vấn đề gì.
Mai's first question can concern Nam's availability. Nam then separates availability (có thể đến) from permission (được vào). Mai cites an explicit rule with được phép and gives advice with nên. Replacing the first có thể with được phép would ask who authorized Nam to attend, not whether attendance is feasible.
Common Mistakes
1. Using có thể for learned know-how.
❌ Con tôi có thể bơi rồi.
Misleading if the intended meaning is ‘My child has learned how to swim’; this can instead emphasize current capacity.
✅ Con tôi biết bơi rồi.
My child knows how to swim now.
Use biết + verb when acquiring a skill is the point.
2. Using có thể where permission is the issue.
❌ Nhân viên có thể vào khu vực này.
Ambiguous for a rule: it may merely say that employees are able to enter.
✅ Chỉ nhân viên được phép vào khu vực này.
Only employees are permitted to enter this area.
The repair names authorization explicitly.
3. Reversing the scope of không.
❌ Tôi không thể đi nếu trời tạnh.
Wrong for ‘I may not go even if it clears up’: this says going is impossible if it clears.
✅ Dù trời tạnh, tôi vẫn có thể không đi.
Even if it clears up, I still may not go.
Putting không after có thể makes the negative event one possible outcome.
4. Translating predictive English ‘can’ as ability.
❌ Mùa hè ở đây biết rất nóng.
Incorrect: biết marks learned skill, not a possible recurring condition.
✅ Mùa hè ở đây có thể rất nóng.
Summers here can be very hot.
Key Takeaways
- Có thể covers circumstantial possibility, capacity, and epistemic possibility.
- Learned know-how is normally biết + verb; permission is normally được or explicit được phép.
- Không thể làm means doing is impossible; có thể không làm means not doing is possible.
- Aspect and time markers locate the possibility: có thể đã, có thể đang, sẽ có thể, and đã có thể are not interchangeable.
- The natural Vietnamese modal depends on evidence, authority, circumstances, and interpersonal force—not on one-to-one translation from English.
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Start learning Vietnamese →Related Topics
- Positive Directives with Hãy, Cứ, and Bare PredicatesA2 — Choose among bare predicates, hãy, cứ, mời, address terms, and final particles to shape positive Vietnamese directives.
- Biết plus Verb for Learned AbilityA2 — Use biết before a verb to describe learned know-how, and separate skill from present ability, permission, and opportunity.
- Dám and Willingness to RiskB1 — Use dám to express the courage or nerve to act, and distinguish willingness to risk from ability, permission, and obligation.
- Cũng and Additive ScopeB1 — Use cũng for also, too, and universal free-choice readings, with clear control of its preverbal scope and topic-based focus.