The only 15 letter word that can be spelled without repeating a letter is uncopyrightable。

uncopyrightable(不可赋予版权的)是唯一个由15个完全不重复的字母组成的单词。

youdao

James Grimmelmann, an associate professor at the New York Law School, has a long analysis in which he suggests that the MMSE form is uncopyrightable.

FORBES: Medical Diagnostic Test Taken Down By Copyright Claim