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