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