Èrjíguǎn zhǐ ràng diànliú cháo yí ge fāngxiàng liúdòng, suǒyǐ kěyǐ bǎ jiāoliúdiàn biànchéng zhíliúdiàn.
A diode lets current flow in only one direction, so it can turn alternating current into direct current.
Tips
memory
二 'two' + 极 'pole, electrode' + 管 'tube': a device with two electrodes, named in the age of vacuum tubes. A light-emitting diode is a 发光二极管 (LED), and a transistor is a 三极管.