Multiple onyomi


If a kanji has multiple onyomi, which one do you use? Is there a rule
governing this or can you use any one at any time?




There is no general rule. It depends on the compound in which the kanji
appears. Sometimes even compounds have two readings.

Japanese people themselves (literate ones, that is) sometimes don't know how
to read a personal name or place name.

You cannot pick just any onyomi. For instance 上 in 上手 (jouzu) must be じょう, and
in 上海 (Shanhai: the Chinese city Shangai) it must be しゃん. "Shanzu" or "jouhai"
doesn't make sense.

You have to recognize the compound as a word.

