The other great thing is that it's an unwritten code, which means you get to learn by trial and error.

还有一个很严重的问题就是这没有什么明文的条约。这意味着你只有通过尝试并犯错误来学会它。

youdao

There is an unwritten but clearly understood code of behavior which, if broken, makes the person immediately the object of suspicion.

但有一个不成文的、但人们心照不宣的行为规范，如果有人破坏了这个行为规范，他立刻就会成为人们猜疑的对象。

youdao

The civil code demands great numbers of special regulations, unwritten laws and cases.

民法典是建构和生成的统一，它需要大量的单行法、习惯法和判例的支撑。

youdao

The Navy Seals usually respect an unwritten code of staying out of the public eye.

BBC: Bin Laden unit Seal Team Six punished over video game

Even during the campaign they have stuck to an unwritten code, freely expressing differences but carefully avoiding any escalation into serious conflict.

ECONOMIST: Elections in Northern Ireland

Riders who disregard the unwritten code of conduct become villains.

WSJ: Tour de France: The Divine Comedy of Cycling Etiquette--Bradley Wiggins, Christopher Froome