Ngai is the transliteration of three Chinese surnames in Hong Kong based on Cantonese:
魏, also common in northern China as Wei (pinyin: Wèi)
危, pinyin: Wēi
倪, pinyin: Ní
All three characters are written the same way in both traditional and simplified writing systems.
The native pronunciation of these three characters (disregarding their tonal values) is [ŋɐi]. This causes especial difficulty to speakers of English for two reasons:
The engma [ŋ] as an initial consonant is unknown in English. (However, even in modern Cantonese, the omission of initial engma is considered passable, albeit a mark of careless speech.)
In English, the so-called "long i", which the sound ai usually represents in transliteration, represents a complementary distribution of [aɪ] (as in hide) and [ɐɪ] (as in height); or represents the first diphthong exclusively, depending on region. In both cases, English phonotactics call for the first diphthong in this case. However, in Cantonese the two diphthongs are distinct (in systems of Cantonese romanization the two sounds are represented by aai and ai), and the second diphthong is the appropriate one.
Therefore, individuals with these last names, when speaking English, may for convenience pronounce the last name /ˈnaɪ/ or /ˈaɪ/.
