Diphthong /a / (Nguyên âm đôi /a /) .Unit 14 Diphthong /a / Nguyên âm đôi /a / Introduction /a / is a long vowel sound. It starts with /a:/ and moves to / /. It’s pronounced /a //a /. die /da / fighting / fa t ŋ/ like /la k/ surprise /sər pra z/ why /wa / childhood / t a ldh d/ high /ha / tour guide /t ər night /na t/ a d/.