Tiếng Việt · Word Attested

mất công

[mət̚˧˦ kəwŋ͡m˧˧]

In real, traceable use. Part of the curated seed collection; community review is coming.

Sense 1

Both English Tiếng Việt

Meaning · English

(verb) to put one's effort (into something that turns out to useless or not needed)

Nghĩa · Tiếng Việt

làm việc vô ích

Machine-translated — suggest a fix

Where it’s used: Used Toàn quốc & hải ngoại · Vietnam-wide & diaspora

Examples

Tối qua mất công cày bài cả đêm mà sáng ra đề dễ ẹt.Man, last night I put all my effort into studying but (it turned out that) the test this morning was piss easy.

Wiktionary example (CC BY-SA 4.0)

Sources & notes

Imported from Wiktionary (CC BY-SA 4.0, retrieved 2026-07-29); community review pending. source ↗

Sense 2

Both English Tiếng Việt

Meaning · English

(adjective) useless

Nghĩa · Tiếng Việt

vô ích

Machine-translated — suggest a fix

Examples

chuyện mất cônguseless things, useless affairs.

Wiktionary example (CC BY-SA 4.0)

Common questions

What does “mất công” mean?

(verb) to put one's effort (into something that turns out to useless or not needed)

Is “mất công” formal or informal?

mất công is generally informal.