The Vietnamese word for sky is
trời

Translations for sky and their definitions

trời	©
1. n. the sky
ngoài trời - outdoor(s)
2. n. weather
trời nóng/mát/lạnh - it's hot/cool/cold
Trời đẹp nhỉ? - The weather is great, isn't it?
3. n. (sometimes capitalized) a generic deification of the sky that is said to be able to grant "natural gifts" (talent, good weather, etc.) and deal heavenly "punishments" (storms, lightning, etc.); he may
Bắc thang lên mà hỏi ông trời! - Go find a damn ladder to go up and ask the heavenly lord!
bị trời đánh - to be struck by Heaven; to be vanquished by divine wrath
trời đánh tránh bữa ăn - even the heavenly lord knows better not to strike at meal times; don't cause ruckuses at meal times
Con cóc là cậu ông trời,Nếu ai đánh cóc thì trời đánh cho. - The Toad is the Heavenly Lord's boss,If you strike him, the Lord will strike you.
4. adj. (of anseriforms) wild
ngỗng trời - a wild goose
5. adj. Used after ngày, tháng, or năm to emphasize a lengthy duration
mười ngày trời - a full ten days
gần ba năm trời - almost a full three years
6. interj. (colloquial) good Lord!
Trời, sao lại làm như thế? - Good Lord, what did (you/he/she/it) do that for?