Nouns ending in -s, -x, -z, -ch, or -sh add -es to form the plural. This makes the word easier to pronounce.
Parenthesis is regular. It follows the -es Addition rule.
Use plural verbs: "The parenthesises are ready" (not "is ready").
Yes. The plural parenthesises is standard across all English variants.
The word parenthesis follows the standard English pluralization rule. When forming the plural, parenthesis becomes parenthesises. This follows the -es Addition pattern, which is one of the most common plural rules in English.
Understanding why parenthesis becomes parenthesises helps with spelling and pronunciation. Nouns ending in -s, -x, -z, -ch, or -sh add -es to form the plural. This makes the word easier to pronounce.
When using parenthesises in writing, remember that it functions as a plural noun in sentences. It pairs with plural verbs and pronouns. For example: "The parenthesises are ready" (not "is ready"). This subject-verb agreement is essential for grammatical correctness.