A part number (often abbreviated PN, P/N, part no., or part #) is an identifier of a particular part design used in a particular industry. Its purpose is to simplify reference to that part. A part number unambiguously identifies a part design within a single corporation, and sometimes across several corporations.

For example, when specifying a screw, it is easier to refer to "HSC0424PP" than saying "Hardware, screw, machine, 4-40, 3/4" long, pan head, Phillips". In this example, "HSC0424PP" is the part number, and it may be prefixed in database fields as "PN HSC0424PP" or "P/N HSC0424PP".

The part design versus instantiations of it
As a part number is an identifier of a part design (independent of its instantiations), a serial number is a unique identifier of a particular instantiation of that part design. In other words, a part number identifies any particular (physical) part as being made to that one unique design; a serial number, when used, identifies a particular (physical) part (one physical instance), as differentiated from the next unit that was stamped, machined, or extruded right after it. This distinction is not always clear, as natural language blurs it by typically referring to both part designs, and particular instantiations of those designs, by the same word, "part(s)". Thus if you buy a muffler of P/N 12345 today, and another muffler of P/N 12345 next Tuesday, you have bought "two copies of the same part", or "two parts", depending on the sense implied.

A serial number is a unique identifier assigned incrementally or sequentially to an item, to uniquely identify it.

Serial numbers aren't necessarily in base 10, so they may contain digits taken from the Latin alphabet for example. It may entirely be a character string, and it may contain other typographical symbols.

Applications of serial numbering

Serial numbers identify otherwise identical individual units with many, obvious uses. Serial numbers are a deterrent against theft and counterfeit products, as they can be recorded, and stolen or otherwise irregular goods can be identified. Banknotes and other transferable documents of value bear serial numbers to assist in preventing counterfeiting and tracing stolen ones.

Serial numbers may be used to identify individual physical or intangible objects (e.g., computer software or the right to play an online multiplayer game). The purpose and application is different. A software serial number, otherwise called product key, is usually not embedded in the software, but is assigned to a specific user with a right to use the software. The software will function only if a potential user enters a valid product code. The vast majority of possible codes are rejected by the software. If an unauthorised user is found to be using the software, the legitimate user can be identified from the code. It is usually not impossible, however, for an unauthorised user to create a valid but unallocated code either by trying many possible codes, or reverse engineering the software; use of unallocated codes can be monitored if the software makes an Internet connection.

Other uses of the term
The term "serial number" is sometimes used for codes which do not identify a single instance of something. For example, the International Standard Serial Number or ISSN used on magazines and other periodicals, an equivalent to the International Standard Book Number (ISBN) applied to books, is serially assigned not to each individual copy but to an issue of a periodical. It takes its name from the library science use of the word "serial" to mean a periodical.

SKU
In the field of inventory management, a stock keeping unit (SKU /ˌɛsˌkeɪˈjuː, ˈsk(j)uː/) is a distinct type of item for sale,[1] such as a product or service, and all attributes associated with the item type that distinguish it from other item types. For a product, these attributes could include manufacturer, description, material, size, color, packaging, and warranty terms. When a business takes inventory of its stock, it counts the quantity it has of each SKU.

SKU can also refer to a unique identifier or code that refers to the particular stock keeping unit. These codes are not regulated or standardized. When a company receives items from a vendor, it has a choice of maintaining the vendor's SKU or creating its own. This makes them distinct from Global Trade Item Number (GTIN), which are standard, global, tracking units. Universal Product Code (UPC), International Article Number (EAN), and Australian Product Number (APN) are special cases of GTINs.

EAN, Art. Nr.
The International Article Number (also known as European Article Number or EAN) is a standard describing a barcode symbology and numbering system used in global trade to identify a specific retail product type, in a specific packaging configuration, from a specific manufacturer. The standard has been subsumed in the Global Trade Item Number standard from the GS1 organization; the same numbers can be referred to as GTINs and can be encoded in other barcode symbologies defined by GS1. EAN barcodes are used worldwide for lookup at retail point of sale, but can also be used as numbers for other purposes such as wholesale ordering or accounting.

The most commonly used EAN standard is the thirteen-digit EAN-13, a superset of the original 12-digit Universal Product Code (UPC-A) standard developed in 1970 by George J. Laurer.[1] An EAN-13 number includes a 3-digit GS1 prefix (indicating country of registration or special type of product). A prefix with a first digit of "0" indicates a 12-digit UPC-A code follows. A prefix with first two digits of "45" or "49" indicates a Japanese Article Number (JAN) follows.

The less commonly used 8-digit EAN-8 barcode was introduced for use on small packages, where EAN-13 would be too large. 2-digit EAN-2 and 5-digit EAN-5 are supplemental barcodes, placed on the right-hand side of EAN-13 or UPC. These are generally used for periodicals like magazines[2] or books,[3] to indicate the current year's issue number; and weighed products like food, to indicate the manufacturer's suggested retail price.

Global Trade Item Number (GTIN) is an identifier for trade items, developed by GS1.[1] Such identifiers are used to look up product information in a database (often by entering the number through a barcode scanner pointed at an actual product) which may belong to a retailer, manufacturer, collector, researcher, or other entity. The uniqueness and universality of the identifier is useful in establishing which product in one database corresponds to which product in another database, especially across organizational boundaries.

The GTIN standard has incorporated the International Standard Book Number (ISBN), International Standard Serial Number (ISSN), International Standard Music Number (ISMN), International Article Number (which includes the European Article Number (EAN) and Japanese Article Number) and some Universal Product Codes (UPCs), into a universal number space.

GTINs may be 8, 12, 13 or 14 digits long, and each of these four numbering structures are constructed in a similar fashion, combining Company Prefix, Item Reference and a calculated Check Digit (GTIN-14 adds another component- the Indicator Digit, which can be 1-8). GTIN-8s will be encoded in an EAN-8 barcode. GTIN-12s may be shown in UPC-A, ITF-14, or GS1-128 barcodes. GTIN-13s may be encoded in EAN-13, ITF-14 or GS1-128 barcodes, and GTIN-14s may be encoded in ITF-14 or GS1-128 barcodes. The choice of barcode will depend on the application; for example, items to be sold at a retail establishment could be marked with EAN-8, EAN-13, UPC-A or UPC-E barcodes.

The EAN-8 code is an eight-digit barcode used usually for very small articles, such as chewing gum, where fitting a larger code onto the item would be difficult. Note: the equivalent UPC small format barcode, UPC-E, encodes a GTIN-12 with a special Company Prefix that allows for "zero suppression" of four zeros in the GTIN-12. The GS1 encoding and decoding rules state that the entire GTIN-12 is used for encoding and that the entire GTIN-12 is to be delivered when scanned.

Format and encodings
Name - Former names - Barcode symbologies
GTIN-14 (used for wholesale shipments, not retail point of sale) - EAN/UCC-14, SCC-14, DUN-14,[3] UPC Case Code, UPC Shipping Container Code - GS1-128, GS1 Databar, ITF-14
GTIN-13 - EAN, EAN·UCC-13, JAN (subset) - EAN-13
GTIN-12 - EAN·UCC-12, UCC-12 - UPC-A, UPC-E (condensed to 6 digits)
GTIN-8 - EAN/UCC-8 - EAN-8
Note that GTIN-12 and GTIN-13 numbers can be encoded as GTIN-13 or GTIN-14 by adding initial padding zeroes. For GTIN-14, this indicates a "packaging level" of a single item.

The numbering structure is as follows:

T1 - Indicator digit, used for GTIN-14, "1" to "8" indicates a packaging level and "9" a variable measure item. Zero in this position is not considered an Indicator Digit, but rather a pad or fill zero. There is however, no worldwide consensus on which number indicates which packaging level and no significance should be built into this number.
T2 through T13 GS1 Company Prefix & Item (product or service) reference number. The GS1 Company Prefix is allocated to the member company and the Item Reference is allocated by the user company. The length of each of these elements varies in length depending on the length of the allocated GS1 Company Prefix. Each different type of trade item is allocated a different number and, for ease of administration, it is recommended that companies do this sequentially (001, 002, 003, etc.).
T14 is a check digit, which follows the standard modulo 10 calculation.[4]
All books and serial publications sold internationally (including those in U.S. stores) have GTIN (GTIN-13) codes. The book codes are either constructed by prefixing the old 10-digit ISBN with 978, and recalculating the trailing check digit, or from 1 January 2007 issued as thirteen digits starting with 978 (eventually 979 as the 978 ranges are used up).

Each type of trade item is given its own GTIN, with the understanding that there is a potential need to retrieve predefined information from such items; this product or service may be priced, ordered, or invoiced at any point in the supply chain. This includes individual items as well as all of their different packaging configurations.

Source: Wikipedia