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