unwritten

形容词 unwritten:

1. based on custom rather than documentation- J.L.T.C.Spence
2. using speech rather than writing
   同义词：oral
3. said or done without having been planned or written in advance
   同义词：ad-lib, spontaneous

1. It's an unwritten law around here that everyone fetches his own coffee, even the managers.
   这儿有一条不成文法，即每人自己去取咖啡，哪怕是经理也是如此。
2. A body of unwritten religious precepts.
   教义一整套非书面的宗教概念
3. Britain has an unwritten constitution, and the United States has a written constitution.
   英国有不成文的宪法，美国有成文的宪法。