(1) Prototype - hardware - A specification-compliant production readiness demonstration model developed under engineering supervision that represents what manufacturing should replicate. All design engineering and production engineering must be complete, and the assembly must be under configuration control. (Fairley 2009, p 74-75), (Forsberg, Mooz, Cotterman 2005, p 432)
(2) Prototype - software - A term currently with multiple meanings. A “rapid prototype” is usually a software requirements demonstration model, which provides a simulated representation of the software functionality and operator interface. The model facilitates early buyer-developer agreement on the design approach. A software prototype may also be a technical demonstration model. Except with “Evolutionary Prototypes,” the code is usually discarded once the model has served its purpose. (Forsberg, Mooz, Cotterman 2005, p 432)
(3) Prototype - software - Software prototypes are constructed to investigate a situation or to evaluate a proposed approach to solving a technical problem. ... When building a prototype, we keep the knowledge we have gained but we do not use the code in the deliverable version of the system (Fairley 2009, p 74-75)
(1) and (2) Forsberg, K., H. Mooz, H. Cotterman. 2005. Visualizing Project Management, 3rd Ed., John Wiley and Sons.
(1) and (3) Fairley, R. 2009. Managing and Leading Software Projects. Hobken, NJ, USA: John Wiley & Sons.