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