# Bất + root / vô + root: un- / -less in Vietnamese (B2)

> Many Sino-Vietnamese words, the words of Chinese origin that fill news and official writing, have a negative part in front, like English un-, non- or…

Source: https://vietnamesebuddy.com/grammar/bat-vo-negating/ · Updated 2026-10-17

**un- / -less**

Pattern: `bất + [Sino-Vietnamese root] · vô + [Sino-Vietnamese root] · phi + [Sino-Vietnamese root]`

Level: B2 (our estimate) · Register: formal

Typed without accents: bat, vo

Many Sino-Vietnamese words, the words of Chinese origin that fill news and official writing, have a negative part in front, like English un-, non- or -less. Three are common.

*Bất* means "not": *bất hợp pháp* (illegal), *bất công* (unfair), *bất lợi* (unfavourable), *bất ổn* (unstable). *Vô* means "without": *vô gia cư* (homeless, literally without a home), *vô ích* (useless), *vô trách nhiệm* (irresponsible), *vô hiệu* (void). *Phi* means "non-" and puts something outside a category: *phi chính phủ* (non-governmental), *phi lợi nhuận* (non-profit).

They join only Sino-Vietnamese roots, and the result is one fixed word that you learn whole. You can't build new ones from everyday native words: "not tasty" is *không ngon*, never *bất ngon*. Some are so fixed that the parts no longer show: *bất động sản*, literally "things that don't move", is real estate.

You'll meet them most in news reports, laws and official notices. Several are everyday words too: *vô lý* (unreasonable), *bất lịch sự* (rude), *vô duyên* (tactless, awkward). When you're not sure a word exists, *không* + the word is the safe spoken choice: *không hợp pháp*, *không công bằng*.

## Examples

- Hơn 100 lao động cư trú bất hợp pháp ở nước ngoài đã bị trục xuất về nước. — More than 100 workers living abroad illegally have been deported home.
- Thành phố mở thêm hai điểm tạm trú cho người vô gia cư trong mùa mưa. — The city has opened two more temporary shelters for homeless people during the rainy season.
- Nhiều tổ chức phi chính phủ đã tham gia cứu trợ người dân vùng lũ. — Many non-governmental organisations have joined the relief effort for people in the flood areas.
- Hợp đồng ký không đúng thẩm quyền có thể bị tuyên bố vô hiệu. — A contract signed without the proper authority may be declared void.

Previous in How words are built: [Three- and four-syllable doubles intensify: vội vội vàng vàng](https://vietnamesebuddy.com/grammar/redup-intense/)

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