准线

准线	zhǔn xiàn	(math.) directrix (of a conic section) / (engineering, construction etc) reference line
准	zhǔn	to allow / to grant / in accordance with / in the light of
准	zhǔn	accurate / standard / definitely / certainly / about to become (bride, son-in-law etc) / quasi- / para-
线	xiàn	variant of 线
线	xiàn	thread / string / wire / line / CL:条,股,根 / (after a number) tier (unofficial ranking of a Chinese city)