Sanskrit generally connotes several Old Indo-Aryan language varieties.[27][28] The most archaic of these is the Vedic Sanskrit found in the Rigveda, a collection of 1,028 hymns composed between 1500 BCE and 1200 BCE by Indo-Aryan tribes migrating east from what are today Afghanistan across northern Pakistan and into northwestern India.[29][30] Vedic Sanskrit interacted with the preexisting ancient languages of the subcontinent, absorbing names of newly encountered plants and animals; in addition, the ancient Dravidian languages influenced Sanskrit's phonology and syntax.[31] Sanskrit can also more narrowly refer to Classical Sanskrit, a refined and standardized grammatical form that emerged in the mid-1st millennium BCE and was codified in the most comprehensive of ancient grammars,[e] the Aṣṭādhyāyī ('Eight chapters') of Pāṇini.[32] The greatest dramatist in Sanskrit, Kālidāsa, wrote in classical Sanskrit, and the foundations of modern arithmetic were first described in classical Sanskrit.[f][33] The two major Sanskrit epics, the Mahābhārata and the Rāmāyaṇa, however, were composed in a range of oral storytelling registers called Epic Sanskrit which was used in northern India between 400 BCE and 300 CE, and roughly contemporary with classical Sanskrit.[34] In the following centuries, Sanskrit became tradition-bound, stopped being learned as a first language, and ultimately stopped developing as a living language.[9]