# Bởi: by (in written passives) in Vietnamese (B2)

> In written Vietnamese, bởi can name what lies behind an action in a sentence with được or bị, much like English "by": Thành phố bị chia cắt bởi hai con…

Source: https://vietnamesebuddy.com/grammar/boi-passive/ · Updated 2026-10-17

**by (in written passives)**

Pattern: `[subject] + được / bị + [verb] + bởi + [cause]`

Level: B2 (our estimate) · Register: formal · Medium: written

Typed without accents: boi

In written Vietnamese, *bởi* can name what lies behind an action in a sentence with *được* or *bị*, much like English "by": *Thành phố bị chia cắt bởi hai con sông lớn.* The city is divided by two large rivers. The order is the thing affected, then *được* (for something welcome or neutral) or *bị* (for something unwelcome), then the verb, and *bởi* with the cause at the end.

*Bởi* is at home with causes that aren't people: a river, a storm, a factor, the market. *Khu vực này được bao quanh bởi rừng ngập mặn.* This area is surrounded by mangrove forest. You meet it in news and reports, and very often in university papers, where *bị ảnh hưởng bởi* (is affected by) and *được quyết định bởi* (is determined by) are stock phrases.

When the doer is a person or an organisation, standard Vietnamese prefers *do*, placed before the doer and the verb: *Dự án do Sở Xây dựng thực hiện.* The project is carried out by the Department of Construction. *Bởi* with people is common in papers and in news translated from English, but editors often change it to *do*.

In conversation, people rarely use either. They say who did it in an ordinary active sentence: *Sở Xây dựng làm dự án này.* For a cause, they use *vì* or *do*: *Đường ngập vì mưa lớn.* On its own, *bởi*, or *bởi vì*, also means "because"; that's a different use.

## Examples

- Khu bảo tồn được bao quanh bởi rừng ngập mặn và các đầm nuôi tôm. — The reserve is surrounded by mangrove forest and shrimp ponds.
- Nhiều tuyến đường ven biển bị chia cắt bởi lũ trong tuần qua. — Many coastal roads were cut off by floods over the past week.
- Kết quả học tập của sinh viên bị ảnh hưởng bởi nhiều yếu tố, trong đó có thu nhập gia đình. — Students' academic results are affected by many factors, including family income.
- Giá nông sản chủ yếu được quyết định bởi cung và cầu trên thị trường. — Farm prices are mainly determined by supply and demand in the market.

## Compare

- [Made or written by: do + doer + verb](https://vietnamesebuddy.com/grammar/do-passive-agent/): by (the doer)

Previous in Là, có, and how verbs work together: [Verbs that take đến: ảnh hưởng đến, liên quan đến](https://vietnamesebuddy.com/grammar/den-verbs/)
Next in Là, có, and how verbs work together: [Choosing or taking as: bầu / cử / chọn / lấy … làm](https://vietnamesebuddy.com/grammar/bau-lam/)

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