A coLUmn in a database table containing vaLUes that are also found in some primary key coLUmn (of a different table). By extension, any reference to entities of a different type. Some RDBMSs allow a coLUmn to be explicitly labelled as a foreign key and only allow vaLUes to be inserted if they already exist in the relevant primary key coLUmn. [Is it still a foregn key if the primary key is in a different coLUmn in the _same_ table?] (2005-01-14)
