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