轨迹
guǐjī · HSK 7
track
🛤️ 轨 = rail + 迹 = trace; the traced path along the rails = a trajectory or orbit
轨 originally meant the ruts a cart's wheels carve into a road, later any rail or track. 迹 means a footprint or mark left behind. Together they name the path an object follows: a train's track, a planet's orbit, a moving point's locus.