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