How did Vedic Sanskrit differ from later Classical Sanskrit?

Vedic Sanskrit, the most archaic stage of Old Indo-Aryan, differs from Classical Sanskrit primarily through its greater linguistic fluidity and the presence of grammatical forms that were later simplified or discarded.12

The transition to Classical Sanskrit was formalized by the grammarian Pāṇini, whose work, the Aṣṭādhyāyī, established the linguistic standards for the "cultivated" or "purified" language. Key differences include:13

• Verb System: Vedic Sanskrit featured categories that later fell into disuse, such as the injunctive (used to denote general truths) and a more frequent use of the subjunctive. Classical Sanskrit retained the injunctive only in specific negative commands and largely replaced the subjunctive with the optative and future forms.2
• Morphology: Early Vedic forms, such as the nominative plural ending -āsas, were gradually replaced by the more standard -ās found in later texts. Similarly, various early infinitive and gerundive types were standardized or eliminated in favor of the forms recognized by Pāṇini.2
• Standardization: While Vedic Sanskrit was a sacred language (chandas) with dialectal variations, Classical Sanskrit became a highly regulated medium for literature, philosophy, and technical treatises, defined by Pāṇini’s strict grammatical rules.23