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