Social security numbers are used for the purpose of identification whether in obtaining your medical information and records, or paying out benefits to your beneficiaries. (lifeinsure.com)
There is no inherent linear navigation indicator which could be used for the same purpose that page number is used in the printed document world. (safaribooksonline.com)
This three - digit number is used by merchants as a way to verify that the cardholder is present at the purchase. (sapling.com)