开集

开集	kāi jí	open set (math.)
开	kāi	to open (transitive or intransitive) / (of ships, vehicles, troops etc) to start / to turn on; to put in operation; to operate; to run / to boil / to write out (a prescription, check, invoice etc) / (directional complement) away; off / carat (gold) / abbr. for Kelvin, 开尔文 / abbr. for 开本, book format
集	jí	to gather / to collect / collected works / classifier for sections of a TV series etc: episode