Prototypes or prototypical instances combine the most representative attributes of a category. It is the best exemplar among the members of a category and serves as a cognitive reference point with respect to which the surrounding "poorer" instances are categorized.
A prototype can also refer to a test machine or program which is designed for demonstration purposes and is produced in order to understand the problems which may occur when a machine is put into production.
NOTE: see: Categorization, Semantics
wikipedia.org dumped 2003-03-17 with terodump