tại sao
[taːj˧˨ʔ saːw˧˧]
In real, traceable use. Part of the curated seed collection; community review is coming.
Adverb
Where it’s used:
Used
Toàn quốc & hải ngoại · Vietnam-wide & diaspora
Examples
Tại sao mày làm vậy?Why did you do that?
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 ↗
Common questions
What does “tại sao” mean?
(adverb) why
Is “tại sao” formal or informal?
No register label has been reviewed yet — treat it as neutral and check the usage notes above.