Serial number

A serial number is a unique number used for identification. Serial numbers are made in such a way that they change by a fixed discrete integer value, each time a new serial number is needed. Most people refer to any identifier that has numbers and letters in it as a serial number and that can be used to pick a certain item of a large number of items. Not every numerical identifier is a serial number; identifying numbers which are not serial numbers are sometimes called nominal numbers.

Sequence numbers are almost always non-negative, and typically start at zero or one.