Nouns ending in a consonant followed by -y change the -y to -ies in the plural form.
Entirety is regular. It follows the -ies Conversion rule.
Use plural verbs: "The entireties are ready" (not "is ready").
Yes. The plural entireties is standard across all English variants.
The word entirety follows the standard English pluralization rule. When forming the plural, entirety becomes entireties. This follows the -ies Conversion pattern, which is one of the most common plural rules in English.
Understanding why entirety becomes entireties helps with spelling and pronunciation. Nouns ending in a consonant followed by -y change the -y to -ies in the plural form.
When using entireties in writing, remember that it functions as a plural noun in sentences. It pairs with plural verbs and pronouns. For example: "The entireties are ready" (not "is ready"). This subject-verb agreement is essential for grammatical correctness.