The invention is based on a ring gear with teeth (10) and tooth gaps (12), in which the teeth (10) can be brought via tooth flanks (14) into engagement with a corresponding pinion. It is proposed that the tooth flanks (14), after a final engagement point (16) of the pinion, from the tooth head (18) toward the tooth base (20), compared to standard tooth flanks (22), are made to approximate a trochoid (24, 26), described by the pinion and projected into a normal section.