This noun follows the standard English plural rule: simply add -s to the singular form.
Keystone is regular. It follows the Standard -s rule.
Use plural verbs: "The keystones are ready" (not "is ready").
Yes. The plural keystones is standard across all English variants.
The word keystone follows the standard English pluralization rule. When forming the plural, keystone becomes keystones. This follows the Standard -s pattern, which is one of the most common plural rules in English.
Understanding why keystone becomes keystones helps with spelling and pronunciation. This noun follows the standard English plural rule: simply add -s to the singular form.
When using keystones in writing, remember that it functions as a plural noun in sentences. It pairs with plural verbs and pronouns. For example: "The keystones are ready" (not "is ready"). This subject-verb agreement is essential for grammatical correctness.