括线

括线	kuò xiàn	(math.) vinculum
括	kuò	(bound form) to tie up; to tighten up / (bound form) to include; to comprise / to put (text) in brackets / Taiwan pr. [gua1]
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)