Avestan, also known historically as Zend, refers to two languages Old Avestan and Younger Avestan. The languages are known only from their use as the language of Zoroastrian scripture, from which they derive their name. Both are early Iranian languages, a branch of the Indo-Iranian languages within the Indo-European family. Its immediate ancestor was the Proto-Iranian language, a sister language to the Proto-Indo-Aryan language, with both having developed from the earlier Proto-Indo-Iranian. As such, Old Avestan is quite close in grammar and lexicon with Vedic Sanskrit.