adj.非书面的，不成文的，惯常的(法律、规定、协议等)，未写的，未写完的

There's an unwritten rule that you don't talk about politics at the dinner table.
有一条不成文的规定，就是在餐桌上不要谈论政治。
The unwritten social contract between the generations is breaking down.
代际之间不成文的社会契约正在瓦解。
She was well aware of the unwritten code of conduct in her profession.
她很清楚自己职业中不成文的行为准则。
The company has an unwritten policy of promoting from within.
这家公司有一项不成文的政策，即从内部提拔人才。
There are unwritten rules about how to behave at a funeral.
在葬礼上如何表现有一些不成文的规则。
The unwritten law of the jungle is survival of the fittest.
丛林法则这条不成文的法律就是适者生存。
He broke one of the team's unwritten rules by speaking to the press.
他违反了团队中一条不成文的规则，向媒体透露消息。
The unwritten agreement between us was that we would share the expenses.
我们之间有一个不成文的协议，就是共同承担费用。
It's an unwritten tradition that the eldest son inherits the family business.
长子继承家族企业的传统是不成文的。
There's an unwritten understanding that we won't interfere in each other's personal lives.
我们之间有一种不成文的理解，那就是不干涉彼此的私生活。