unwritten
/ˌʌnˈrɪtən/adjective
1- not recorded in writing未写下的; 无文字记录的：
documenting unwritten languages
记录无文字语言。
1.1
- (especially of a law) resting originally on custom or judicial decision rather than on statute（尤指法律）未成文的：
an unwritten constitution.
未成文宪法。
1.2
- (of a convention) understood and accepted by everyone, although not formally established惯例的, 因袭的：
the unwritten rules of social life.
社会生活中的不成文规定。