Family of Scale Models/Prototypes

 

Mockup
Built to demonstrate relations of adjacent parts.
Built to scale; need not work.

Working Model
Built to illustrate the concept functioning -- especially the relative motions of connected moving parts.
Not always to full scale; probably does not operate optimally.

Engineering Prototype
Built to demonstrate important design parameters; used to test reliability, speed, accuracy, etc.
Usually hand built; often full scale; durable to withstand testing.

Production Prototype
Built to illustrate performance requirements met, production problems resolved, quality control achievable, etc.
Built as like the mass produced item as possible, differing only in the volume level of production.