Asha (aša) is the Avestan language term (corresponding to Vedic language ṛta) for a concept of cardinal importance to Zoroastrian theology and doctrine. In the moral sphere, aša/arta represents what has been called "the decisive confessional concept of Zoroastrianism." The opposite of Avestan aša is druj, "lie."
The significance of the term is complex, with a highly nuanced range of meaning. It is commonly summarized in accord with its contextual implications of 'truth' and 'right(eousness)', 'order' and 'right working'. For other connotations, see meaning below.
Its Old Persian equivalent is arta-. In Middle Iranian languages the term appears as ard-.
The word is also the proper name of the divinity Asha, the Amesha Spenta that is the hypostasis or "genius" of "Truth" or "Righteousness". In the Younger Avesta, this figure is more commonly referred to as Asha Vahishta (Aša Vahišta, Arta Vahišta), "Best Truth". The Middle Persian descendant is Ashawahist or Ardwahisht; New Persian Ardibehesht or Ordibehesht. In the Gathas, the oldest texts of Zoroastrianism and thought to have been composed by the prophet himself, it is seldom possible to distinguish between moral principle and the divinity. Later texts consistently use the 'Best' epithet when speaking of the Amesha Spenta, only once in the Gathas is 'best' an adjective of aša/arta.
Read more about Asha: Etymology, Meaning, Fire As The Agent of Truth, In Eschatology and Soteriology, In Relationship To The Other Amesha Spentas, In The Zoroastrian Calendar, Iconography, In Proper Names