Editing Part number (section)

==The part design versus instantiations of it==
[[File:RAFI FTKS -- part number stampings.jpg|thumb|400px|Parts marked with assigned part numbers]]
As a part number is an identifier of a part ''design'' (independent of its [[wikt:instantiation#Noun|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 [[word sense|sense]] implied.