open vowel

(phonetics 语音) vowel made with the tongue lowered considerably from the roof of the mouth, eg / B:/,/ C/ 开元音（发音时舌位较低）如 / B:/、/ C/.

opague, opal, opalescence, opalescent, opaque, opaquely, opaqueness, OPEC, open, open an account, open cheque, open day, open letter, open out, open prison, open question, open sandwich, open to, open up, open verdict, open-air, open-and-shut, open-ended, open-eyed, open-handed, open-handedly, open-handedness, open-heart surgery, open-hearted, open-minded, open-mindedness, open-mouthed, open-plan, open-work, opencast, opener, opening, opening night, opening-time, openly,