1) Having distinct features 
In mathematics, an expression is well-defined if it is unambiguous and its objects are independent of their representation. More simply, it means that a mathematical statement is sensible and definite. In particular, a function is well-defined if it gives the same result when the form (the way in which it is presented) is changed but the value of ...
[adj] - accurately stated or described
adjective accurately stated or described; `a set of well-defined values`