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