to get sth open by tapping or striking it / (figuratively, when followed by sth like ∼的大門|∼的大门[xx5 de5 da4 men2]) to open the door to ~ / to gain access to ~
to open / to start / to turn on / to boil / to write out (a prescription, check, invoice etc) / to operate (a vehicle) / carat (gold) / abbr. for Kelvin, 開爾文|开尔文[Kai1 er3 wen2] / abbr. for 開本|开本[kai1 ben3], book format