A serial number is a unique number

Number

A number is a mathematical object used to count and measure. In mathematics, the definition of number has been extended over the years to include such numbers as zero, negative numbers, rational numbers, irrational numbers, and complex numbers....

 assigned for identification

Identification (information)

The function of identification is to map a known quantity to an unknown entity so as to make it known. The known quantity is called the identifier and the unknown entity is what needs identification. A basic requirement for identification is that the Id be unique. Ids may be scoped, that is, they...

 which varies from its successor

Successor

A successor can refer to* Someone who, or something which succeeds or comes after * Successor , an American Thoroughbred racehorseIn history:* The Diadochi, or Successors to Alexander the GreatIn mathematics:...

 or predecessor by a fixed discrete integer

Integer

The integers are formed by the natural numbers together with the negatives of the non-zero natural numbers .They are known as Positive and Negative Integers respectively...

 value. Common usage has expanded the term to refer to any unique alphanumeric

Alphanumeric

Alphanumeric is a combination of alphabetic and numeric characters, and is used to describe the collection of Latin letters and Arabic digits or a text constructed from this collection. There are either 36 or 62 alphanumeric characters. The alphanumeric character set consists of the numbers 0 to...

 identifier for one of a large set of objects, however not every numerical identifier is a serial number; identifying numbers which are not serial numbers are sometimes called nominal number

Nominal number

Nominal numbers are numerals used for identification only. The numerical value is irrelevant, and they do not indicate quantity, rank, or any other measurement.-Definition:...

s. In data processing

Data processing

Computer data processing is any process that a computer program does to enter data and summarise, analyse or otherwise convert data into usable information. The process may be automated and run on a computer. It involves recording, analysing, sorting, summarising, calculating, disseminating and...

 and allied fields in computer science

Computer science

Computer science or computing science is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems...

, the distinction between serial and nominal numbers is an important one.

Sequence numbers are almost always non-negative, and typically start at zero or one.
Serial numbers are valuable in quality control

Quality control

Quality control, or QC for short, is a process by which entities review the quality of all factors involved in production. This approach places an emphasis on three aspects:...

, as once a defect is found in the production of a particular batch of product, the serial number will quickly identify which units are affected.