Final answer:
In Ancient Greek or Latin, the 3rd declension neuter nouns in the plural often have a nominative case ending in '-a' for Latin or '-α'/'-ά' in Ancient Greek. The question likely seeks the number category, which is 'plural' for 'more than one' of the noun.
Step-by-step explanation:
The question "What is the 3rd declension - neuter noun in plural?" pertains to the topic of Ancient Greek or Latin grammar, where nouns are categorized based on their declension and gender. Declensions are sets of patterns that nouns follow for their various forms in different cases. Specifically, in the context of the 3rd declension neuter nouns in these languages, they have unique forms for the nominative plural case which often ends in '-a' in Latin (e.g., 'corpora' from 'corpus') and can end in '-α' or '-ά' in Ancient Greek (e.g., 'σῶματα' from 'σῶμα').
It is worth noting that the question seems a bit unclear. Generally, the terms nominative, vocative, and plural refer to grammatical categories: nominative being a case often used for the subject of a sentence, vocative being used for direct address, and plural being a number category referring to more than one of something. Since the question asks specifically for the neuter noun in the plural, the correct answer would be plural, which is what is being asked about rather than a specific case like nominative or vocative.