Zoroastrianism vs Avestan

Zoroastrianism and Avestan both are nouns.

Word	Noun	Adjective	Verb	Adverb
Zoroastrianism	Yes	No	No	No
Avestan	Yes	Yes	No	No

Zoroastrianism (noun)	Avestan (noun)
system of religion founded in Persia in the 6th century BC by Zoroaster; set forth in the Zend-Avesta; based on concept of struggle between light (good) and dark (evil)	an ancient Iranian language, used as the language of Zoroastrian scripture
	the script in which the ancient Persian language of the Avesta is written

Zoroastrianism (adjective)	Avestan (adjective)
	of or pertaining to the Avesta (sacred text of Zoroastrianism)