are Japanese kanji readings borrowed from Chinese during the Tang dynasty, from the 7th to the 9th centuries; a period which corresponds to the Japanese Nara period. They were introduced by, among others, envoys from Japanese missions to Tang China. Kan-on should not be confused with , which were later phonetic loans.
Kan-on are based on the central Chang'an pronunciation of Middle Chinese. The syllable Kan is a reading of Middle Chinese: 漢 (xanH) as per Japanese phonology, referring to the Han dynasty, which had Chang'an as its capital city. Furthermore, Kan (漢) has also become a description for all things Chinese, e.g., kanji ('Chinese characters').
Kan'on partly displaced the earlier go-on, which were "just imitations of Korean imitations, but Kan-on were imitations of the real thing."
A minority of characters never had their kan-on transmitted to Japan; their kan-on are sometimes reconstructed in Japanese dictionaries although not specifically marked as such. A few dictionaries go as far as to discard attested kan-on in favour of more systematic pronunciations.
Characteristics as compared to go-on
In consonants zi- / ni-, zy- / ny-Kanji神大土地分仏男女万美無二 児人 刃日如若Kan-onsintaitotifunfutudandyobanbibuzizinzituzyozyakuGo-onzindaidodibunbutunannyomanmimunininnitinyonyaku d- / n-b- / m- r-, er
In vowels * / -e -ei / -ai * / -uKanji衣気戯愛解会 絵快 怪外仮 家下 夏化花西 斉体 帝米礼素図怒公 口豆 頭右 有九 久留Kan-onikigiaikaikwaigwaikakwaseiteibeireisotodokoutouiukiuriuGo-onekegeegewekegekegekesaitaimairaisudunukuduukuru -i -i- / -o- -e- / -o- -a- / -o- -a- / -ya- -yoku / -iki音 隠今 金品乙乞遠 園建言 厳越叛発行客白色 拭食直力Kan-oninkinfinitukituwenkengenwetufanfatukaukakufakusyokutyokuryokuGo-ononkonfonotukotuwonkongonwotifonfotugyaukyakubyakusikizikidikiriki -e- / -ya- 京 経形正 声成 静丁 挺定兵平 病名 命 明霊役石 赤寂暦牛月殺文 聞Kan-onkeiseiteifeimeireiekisekirekigiugetusatubunGo-onkyaugyausyauzyautyaudyaufyaubyaumyauryauyakusyakuzyakuryakugugwatisetumon -ing: zheng, cheng, sheng
See also On'yomi: Sino-Japanese readings Go-on: an earlier type of reading Tō-on: a later type of reading Checked tone
References