Message Oracle PLS-00224 - object string must be of type function or array to be used this way

ERRORobject string must be of type function or array to be used this way
CAUSEAn identifier being referenced as a function or an array actually represents an object (a number or date, for example) that cannot be referenced in this way.
ACTIONCheck the spelling and declaration of the identifier. Also confirm that the declaration is placed correctly in the block structure.