A field attribute that automatically stores a unique number for each record as it's added to a table. An AutoNumber field uses the Long data type and has its Attributes property set to dbAutoIncrement. Numbers generated by an AutoNumber field can't be modified. (Also known as a Counter.)
Note For replicated tables in replicated databases, an AutoNumber field is not incremented by 1. Instead, it is assigned a random value between -2,000,000,000 and 2,000,000,000.