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