Part number

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. It refers below

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".

As a part number is an identifier of a part design (independent of its ), 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 business using a part will often use a different part number than the various manufacturers of that part do. This is especially common for catalog hardware, because the same or similar part design (say, a screw with a certain standard thread, of a certain length) might be made by many corporations (as opposed to unique part designs, made by only one or a few).

For example, when referring to a "Hardware, screw, machine, 4-40, 3/4" long, Phillips":

The business using such a screw may buy screws from any of those manufacturers, because each supplier manufactures the parts to the same specification. To identify such screws, the user doesn't want to use any of those manufacturer's part numbers, because

Therefore, the user devises its own part numbering system. In such a system, the user may use the part number "HSC0424PP" for that screw.

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