Unwritten (adjective)

Not put into writing; not recorded or documented.

Origin:

From un- (not) + written (put into writing).

Examples:

1. The rules of the game were unwritten and passed down by word of mouth.
2. The tradition was unwritten and passed down through generations.
3. The law was unwritten and not officially recognized.
4. The history was unwritten and not recorded in any books.
5. The etiquette was unwritten and not formally taught.