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an urban-type settlement in Chelny Raion, Tatar ASSR. Situated on the Zai River (a tributary of the Kama), 55 km southwest of the river landing Naberezhnye Chelny (on the Kama). It has a railroad station on a branch of the Ul’ianovsk-Ufa line. Near Zainsk, in the settlement of Novyi Zai, is the Zai State District Electric Power Plant.