開口音かいこうおん(of Chinese) pronunciation of kanji without a medial between the initial consonant and center vowel(of Japanese) the long "o" vowel arising from combination of the "a" and "u" sounds
合口音ごうこうおん(of Chinese) pronunciation of kanji with a medial between the initial consonant and center vowel(of Japanese) the long "o" vowel arising from combination of the "o" and "u" or "e" and "u" sounds