The word "Gatha" means songs or hymns, the Gathas of Zoroaster consists of 17 songs. 7 in Ahunavaiti (Yasna 28-34), 4 in Ushtavaiti (Yasna 43-46), 4 in Spenta Mainyu Yasna 47-50), 1 in Vohu Khshathra (Yasna 51), 1 in Vahishta Ishti (Yasna 53)