不成文

unwritten (rule)

no; not so / (bound form) not; un-

won't do / unable to / (at the end of a rhetorical question) can that be?

surname Cheng

to succeed / to finish / to complete / to accomplish / to become / to turn into / to be all right / OK! / one tenth

written / statutory

language / culture / writing / formal / literary / gentle / (old) classifier for coins / Kangxi radical 67

unwritten law