Vietnamese do and bởi can introduce a cause, and both can identify the agent responsible for an event. They overlap with English because of, due to, and by, but they are not identical in tone. Do is the ordinary choice for an attributed or objective cause; bởi is more marked and often belongs to careful, formal, or literary phrasing.
These words sit in the same broad relational system as coverbs such as ở, từ, đến, với, bằng, and cho. Many Vietnamese “preposition-like” words developed from verbs and can still head verb-like sequences. Do and bởi are comparatively grammaticalized: learners should recognize the coverb pattern without inventing an independent lexical-verb meaning for every occurrence.
Do for a cause
Use do + noun phrase to attribute an event or condition to a cause. It is especially natural with technical explanations, disruptions, faults, weather, illness, and other circumstances presented as factual causes.
Chuyến bay bị hoãn do thời tiết xấu.
The flight was delayed due to bad weather.
Máy không khởi động được do pin đã hết.
The device won’t start because the battery is dead.
A complete clause can follow do directly. When the cause comes first, do ... nên ... explicitly pairs cause and result.
Do đường bị ngập nên xe buýt đến muộn.
Because the road was flooded, the bus arrived late.
Tôi phải ở nhà do con đang bị sốt.
I have to stay home because my child has a fever.
Plain vì would also be possible in all four examples. The difference is a tendency, not an absolute rule: vì is the default conversational explanation and often includes the speaker’s motivation, whereas do sounds more like causal attribution. Compare the dedicated discussion of vì.
Bởi and bởi vì
Bởi vì + clause is a full, emphatic “because.” It occurs in careful conversation as well as writing, although plain vì is shorter and more frequent in casual answers. Bare bởi + noun/clause is grammatical but tends to sound formal, literary, or rhetorically deliberate.
Tôi đồng ý bởi vì kế hoạch này thực tế hơn.
I agree because this plan is more practical.
Bởi không ai phản đối, đề xuất đã được thông qua.
Since no one objected, the proposal was approved. (formal)
Niềm tin ấy được nuôi dưỡng bởi những việc nhỏ hằng ngày.
That trust is sustained by small everyday actions. (literary/formal)
In ordinary conversation, substituting bare bởi for every vì can sound bookish. Bởi vì is much less marked than bare bởi, but it still gives the causal link more weight.
Naming the agent: do/bởi + actor
Vietnamese does not need a passive construction whenever English uses one. An active clause is often shorter and more natural. When a passive or result-focused clause does name the actor, do and bởi can introduce that actor.
Cây cầu này do một công ty Việt Nam thiết kế.
This bridge was designed by a Vietnamese company.
Bản báo cáo được chuẩn bị bởi nhóm nghiên cứu độc lập.
The report was prepared by an independent research team. (formal)
The common pattern NOUN + do + AGENT + VERB foregrounds the product or outcome while retaining a compact active predicate inside the clause. It is extremely useful in labels, credits, explanations, and formal descriptions. Được/bị + VERB + bởi + AGENT resembles an English be + participle + by passive and is common in formal translated or technical prose, but everyday Vietnamese often prefers an active clause or omits the agent.
Nhóm nghiên cứu độc lập đã chuẩn bị bản báo cáo.
An independent research team prepared the report. (neutral active wording)
Cause, agent, reason, purpose, and source
These relations answer different questions. Keeping them separate prevents several common translation errors.
| Relation | Typical marker | Example |
|---|---|---|
| personal reason or motivation | vì | nghỉ vì mệt — take a break because one is tired |
| attributed cause | do | lỗi do phần mềm — an error caused by software |
| formal cause | bởi / bởi vì | bởi hoàn cảnh — owing to the circumstances |
| agent or author | do / bởi | do Mai viết — written by Mai |
| intended result | để | đến để giúp — come in order to help |
| reported source or standard | theo | theo báo cáo — according to the report |
Compare three superficially similar phrases:
Theo báo cáo, chi phí đã giảm mười phần trăm.
According to the report, costs fell by ten percent.
Báo cáo do phòng tài chính soạn.
The report was drafted by the finance department.
Cuộc họp bị hoãn do báo cáo chưa xong.
The meeting was postponed because the report was not finished.
Theo báo cáo identifies the information source. Do phòng tài chính identifies the author. Do báo cáo chưa xong identifies a cause. The next page treats theo and source reporting in detail.
Position and scope
A causal phrase may come before or after the result. Initial position frames the entire clause; final position often answers a specific request for explanation.
Do mất điện, cửa hàng đóng sớm.
Because of a power outage, the shop closed early.
Cửa hàng đóng sớm do mất điện.
The shop closed early because of a power outage.
An agent phrase normally stays close to the predicate or result it belongs to. Moving it to the beginning may turn it into a contrastive topic and requires context: Do chị Lan phụ trách, phần này tiến triển rất nhanh is naturally causal (“Because Ms. Lan is in charge ...”), not simply “by Ms. Lan.”
The wider coverb map
The same surface position can encode very different relations:
| Phrase | Role | Contrast |
|---|---|---|
| ở nhà | static location | stay at home |
| đến trường | goal | go/come to school |
| từ Hà Nội | source | from Hà Nội |
| với bạn | accompaniment | with a friend |
| bằng xe buýt | means | by bus |
| cho em | recipient | for you |
| do mưa | cause | because of rain |
| trên bàn | spatial relation | on the table |
For complex space, Vietnamese commonly combines a locative coverb with a relational noun: ở trên bàn, ở dưới cầu, ở trong nhà, ở ngoài sân, ở trước cửa, ở sau trường. The relational noun cannot be discarded simply because English uses one preposition.
A dialogue where one marker changes the claim
— Ai viết thông báo này? — Thông báo do phòng nhân sự viết.
— Who wrote this notice? — The notice was written by Human Resources.
— Tại sao có thông báo này? — Vì lịch làm việc thay đổi nên phòng nhân sự mới viết thông báo.
— Why is there this notice? — Human Resources wrote it because the work schedule changed.
In the first answer, do + actor + verb identifies agency. In the second, vì ... nên ... gives the reason for the action and its result. The listener therefore distinguishes the actor who wrote the notice from the changed schedule that motivated the writing.
Register choices
- Do is neutral in notices, reporting, technical explanations, and everyday causal statements.
- Bởi vì is neutral-to-emphatic and works in careful speech and writing.
- Bare bởi for a cause is (formal/literary).
- Bởi + agent is common in (formal/academic) passive-like prose; do + agent + verb is often more idiomatic and compact.
- In (informal) conversation, vì usually sounds easier than bare bởi.
Common Mistakes
1. Using an agent marker for an information source.
❌ Bởi báo cáo, doanh thu đã tăng.
Incorrect for ‘According to the report’; bởi makes the report sound like a cause or agent.
✅ Theo báo cáo, doanh thu đã tăng.
According to the report, revenue increased.
2. Copying an English by-passive when an active clause is more natural.
✅ Bữa tối được mẹ tôi nấu.
Dinner was cooked by my mother. (correct when dinner is the topic or the actor is contrastive)
✅ Mẹ tôi nấu bữa tối.
My mother cooked dinner.
3. Confusing cause with purpose.
❌ Tôi gọi cho bác sĩ do hỏi kết quả.
Incorrect for an intended purpose: do presents a cause, not a goal.
✅ Tôi gọi cho bác sĩ để hỏi kết quả.
I called the doctor to ask about the results.
4. Omitting a relational noun in a location.
❌ Hồ sơ ở bàn.
Incomplete for the ordinary meaning ‘The file is on the desk.’
✅ Hồ sơ ở trên bàn.
The file is on the desk.
5. Treating do and bởi as identical in register.
✅ Bởi kẹt xe nên tôi đến muộn.
Owing to traffic, I arrived late. (formal/literary)
✅ Vì kẹt xe nên mình tới trễ nha.
I’ll be late because of traffic, okay? (informal)
Key Takeaways
- Use do for an attributed cause and in X do Y làm to name an actor or author.
- Use bởi vì for an explicit “because”; bare bởi is more formal or literary.
- Do not confuse an agent (do/bởi), a reported source (theo), and an intended purpose (để).
- Vietnamese often prefers an active clause to a heavy passive copied from English.
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Start learning Vietnamese →Related Topics
- Vì for Reason and PurposeA2 — Use vì to present a reason or motivating interest, and distinguish it from true purpose clauses with để.
- Theo for Following and According ToA2 — Use theo as a verb meaning follow and as a relational marker for sources, standards, paths, and organizing principles.
- Ở Đâu and Đi ĐâuB1 — Distinguish location with ở đâu from destination with đi đâu and place each expression in its natural clause position.
- Sino-Vietnamese Morpheme OrderB1 — Recognize modifier-first order inside many established Sino-Vietnamese compounds while preserving ordinary Vietnamese order in larger phrases.