I'm very confused by the difference between "archetype" and "prototype", and even more baffled when to use which. Can someone clarify?
I will disagree with Robusto and Mr. Disappointment insomuch that the two words have very different meanings. This is copied from my local dictionary and I think it describes the difference well:
While prototype and archetype are often used interchangeably, they really mean quite different things. An archetype is a perfect and unchanging form that existing things or people can approach but never duplicate (: the archetype of a mother), while a prototype is an early, usually unrefined version of something that later versions reflect but may depart from (: a prototype for a hydrogen-fueled car).
In other words, a prototype is a (usually physical) draft. An archetype is an ideal example or theoretical perfect form. Something could correctly be labeled both a prototype and archetype but generally prototypes are inferior to the final product. Their very label of prototype implies that it will be replaced with a different form later in the design process.
The final prototype can be considered the primary modeling example if the object is intended for mass production and a loose usage of "archetype" could apply. Then the meaning would shift from focusing on the prototype and, instead, focusing on the reproductions. As in, the reproductions better faithfully mimic the archetype because if they didn't than the process is flawed. This usage holds no implications about the perfection of the archetype and, therefore, I consider prototype the appropriate word.
Even the other dictionary examples posted in the other examples are not suggesting they are synonyms:
prototype - a first or primitive form
archetype - original pattern from which copies are made
"First form" and "original pattern" are similar but their usages are drastically different.
archetype - an original model or type after which other similar things are patterned; a prototype
Using "prototype" to describe "archetype" works but the usage example helps reveals the difference:
"'Frankenstein' ... 'Dracula' ... 'Dr. Jekyll and Mr. Hyde' ... the archetypes that have influenced all subsequent horror stories" (New York Times).
"Prototype" would be incorrect in that sentence. Here is the same dictionary's definition of prototype:
prototype - an original type, form, or instance serving as a basis or standard for later stages.
The difference in meaning is again hard to see but prototype is a staged type or form: It is "original" in the sense that it came before the next one in sequence. "Archetype" is "original" in the sense that there wasn't anything else before it. You can (and usually do) have a sequence of prototypes; you generally only have one archetype.
They are, for a lot of purposes, synonymous - both coming from Greek and being carried through the years, both referring to an initial foundation, a typical example of something or other.
The difference I would pick up on is that archetype has the benefit of being considered an ideal mould - that is, a fundamental basis which should be taken as an example in future considerations, improvements to the model being few and far between and exclusions of existing features unheard of - whereas prototype could simply be the first mould, for all it works as expected, may be subject to improvement and, in fact, possibly some implementation of it being wrong and in need of correction.
OED: c.1600, from Fr. prototype, from M.L. prototypon, from Gk. prototypon "a first or primitive form," properly neut. sing. of prototypos "original, primitive," from protos "first" (see proto-) + typos "impression" (see type).
ThreFreeDictionary: [French, from Greek prtotupon, from neuter of prtotupos, original : prto-, proto- + tupos, model.]
OED: "original pattern from which copies are made," 1540s, from L. archetypum, from Gk. arkhetypon "pattern, model, figure on a seal," neut. of adj. arkhetypos "first-moulded," from arkhe- "first" (see archon) + typos "model, type, blow, mark of a blow" (see type). Jungian psychology sense of "pervasive idea or image from the collective unconscious" is from 1919.
TheFreeDictionary: [Latin archetypum, from Greek arkhetupon, from neuter of arkhetupos, original : arkhe-, arkhi-, archi- + tupos, model, stamp.]
The two words are synonymous, but I mostly hear archetype used in this sense:
2: An ideal example of a type; quintessence: an archetype of the successful entrepreneur.
And prototype seems mainly used in this sense:
2: An original, full-scale, and usually working model of a new product or new version of an existing product.
I realize that each of these represents the second entry in its second definition, but that's what I hear most often.
EDIT Markdown issue fixed. Thanks, @Alenanno.