An identifier causes an error.

Microsoft Access 97 or later supports some new Visual Basic keywords, so you can no longer use these keywords as identifiers. These keywords are: AddressOf, Decimal, DefDec, Enum, Event, Friend, Implements, RaiseEvent, WithEvents. When you convert a previous-version Access database to Microsoft Access 2000, existing identifiers that are the same as a new Visual Basic keyword will cause a compile error. To fix this problem, change existing identifiers so they are not keywords.