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