Chapter 29: The Dream

Simplified Chinese (Mandarin: China)
噩梦 Èmèng	噩梦 èmèng = 'nightmare'.	The Nightmare
Traditional Chinese (Mandarin: Taiwan)
夢境 Mèngjìng	夢境 mèngjìng = 'dreamland, dream'.	The Dream
Japanese
夢 Yume	夢 yume = 'dream'.	The dream
Korean
꿈 Kkum		The Dream
Vietnamese (Chinese characters show etymology)
Giấc mơ	giấc mơ = 'dream, daydream'.	The Dream
Mongolian (new)
Зүүд Züüd	зүүд züüd = 'dream'.	The Dream

This is where Harry falls asleep in the Divination class and sees Voldemort. Translating this is relatively straightforward.

How is 'the dream' translated?

The Mainland Chinese version translates it as 'nightmare' (噩梦 èmèng).
The Chinese translator from Taiwan uses 夢境 mèngjìng, where 境 jìng means 'territory, place, land'. The meaning is thus literally 'land of dreams', referring to the place you go when dreaming.
The Japanese (夢 yume), Vietnamese (giấc mơ), and Mongolian (зүүд züüd) titles all refer fairly straightforwardly to dreams. Note: although Japanese yume is written 夢, using the same character as the Chinese word mèng, this a Japanese native word etymologically unrelated to the Chinese.

(Detailed notes on the chapter can be found at Harry Potter Lexicon)