diphthongize
verb /ˈdɪfθɒŋaɪz/,  /ˈdɪpθɒŋaɪz/
  /ˈdɪfθɔːŋaɪz/,  /ˈdɪpθɔːŋaɪz/
(British English also diphthongise)
 (phonetics)Verb Forms
| present simple I / you / we / they diphthongize |  /ˈdɪfθɒŋaɪz/,  /ˈdɪpθɒŋaɪz/  /ˈdɪfθɔːŋaɪz/,  /ˈdɪpθɔːŋaɪz/ | 
| he / she / it diphthongizes |  /ˈdɪfθɒŋaɪzɪz/,  /ˈdɪpθɒŋaɪzɪz/  /ˈdɪfθɔːŋaɪzɪz/,  /ˈdɪpθɔːŋaɪzɪz/ | 
| past simple diphthongized |  /ˈdɪfθɒŋaɪzd/,  /ˈdɪpθɒŋaɪzd/  /ˈdɪfθɔːŋaɪzd/,  /ˈdɪpθɔːŋaɪzd/ | 
| past participle diphthongized |  /ˈdɪfθɒŋaɪzd/,  /ˈdɪpθɒŋaɪzd/  /ˈdɪfθɔːŋaɪzd/,  /ˈdɪpθɔːŋaɪzd/ | 
| -ing form diphthongizing |  /ˈdɪfθɒŋaɪzɪŋ/,  /ˈdɪpθɒŋaɪzɪŋ/  /ˈdɪfθɔːŋaɪzɪŋ/,  /ˈdɪpθɔːŋaɪzɪŋ/ | 
- diphthongize something to change a vowel into a diphthong