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