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