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