This noun follows the standard English plural rule: simply add -s to the singular form.
Diphthongise is regular. It follows the Standard -s rule.
Use plural verbs: "The diphthongises are ready" (not "is ready").
Yes. The plural diphthongises is standard across all English variants.
The word diphthongise follows the standard English pluralization rule. When forming the plural, diphthongise becomes diphthongises. This follows the Standard -s pattern, which is one of the most common plural rules in English.
Understanding why diphthongise becomes diphthongises helps with spelling and pronunciation. This noun follows the standard English plural rule: simply add -s to the singular form.
When using diphthongises in writing, remember that it functions as a plural noun in sentences. It pairs with plural verbs and pronouns. For example: "The diphthongises are ready" (not "is ready"). This subject-verb agreement is essential for grammatical correctness.