Avestan (/əˈvɛstən/), or historically Zend, is an umbrella term for two Old Iranian languages: Old Avestan (spoken in the 2nd millennium BCE) and Younger Avestan (spoken in the 1st millennium BCE). They are known only from their conjoined use as the scriptural language of Zoroastrianism, and the Avesta likewise serves as their namesake. Both are early Eastern Iranian languages within the Indo-Iranian language branch of the Indo-European language 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 language; as such, Old Avestan is quite close in both grammar and lexicon to Vedic Sanskrit, the oldest preserved Indo-Aryan language.