Correct

不成文

/ bùchéngwén / 
Strokes

Definition

unwritten (rule)

Example

As an Adjective

not fixed in written form; unwritten; customary

1
Bù
不
chéngwén
成文
héyuē
合约

unwritten agreement

2
Bù
不
chéngwén
成文
de
的
guīju
规矩

unwritten conventions