You can use a reserved word as a quoted user-defined identifier.
The following code declares quoted user-defined identifiers "BEGIN", "Begin", and "begin".
Although BEGIN, Begin, and begin represent the same reserved word, "BEGIN", "Begin", and "begin" represent different identifiers.
SQL> SQL> DECLARE-- ww w . j a v a 2 s .c o m 2 "BEGIN" varchar2(15) := 'UPPERCASE'; 3 "Begin" varchar2(15) := 'Initial Capital'; 4 "begin" varchar2(15) := 'lowercase'; 5 BEGIN 6 DBMS_Output.Put_Line("BEGIN"); 7 DBMS_Output.Put_Line("Begin"); 8 DBMS_Output.Put_Line("begin"); 9 END; 10 / UPPERCASE Initial Capital lowercase PL/SQL procedure successfully completed. SQL>