Model
An abstracted software representation of a hardware or software function, containing some approximation of the set of external connections and some approximation of the internal behavior. The intent of a model could be to document the specification of a function to be implemented/measured, or to serve as part of a checking environment for a design which implements the function, to be compared with the model's execution of any given stimulus, or to deliver an alternate level of detail of the function for some optimized usage.