diphthongal
adjective /dɪfˈθɒŋɡl/, /dɪpˈθɒŋɡl/
/dɪfˈθɔːŋɡl/, /dɪpˈθɔːŋɡl/
(phonetics- combining two vowel sounds or vowel letters, for example the sounds /aɪ/ in pipe /paɪp/ or the letters ou in doubt
compare monophthongal, triphthongal二合元音;复元音;双元音;双元音字母组合