An archetype is a universal theme, story or character which is so fundamental that, regardless of how many times it is used (or misused), it never becomes stale, dated or Cliché. This is the opposite of discredited tropes, which started out as good ideas but were used so often they became cliché. A "pure" archetype is always a partial personality, rather than a rounded character. In fiction or life, an excessively archetypal character is likely to come across as two-dimensional, if not one-dimensional. (And in real life, this sort of character may be mentally ill!)
For example, Star Wars was purposefully built upon Archetypal Characters, to which it owes its longevity. The entire story hinges upon The Hero's Journey, which is an archetypical story.
- Luke Skywalker (The Hero)
- Obi-Wan Kenobi and Yoda (Mentor Archetype)
- Han Solo (The Lancer, Lovable Rogue)
An interesting point is that many tropes could easily be considered archetypes in and of themselves.