As opposed to a simulation, an actual working reconstruction of a thing that can handle the same input and produce the same output as the thing itself.
Articles on KurzweilAI.net that refer to Functional EquivalentInfinite Memory and Bandwidth: Implications for Artificial Intelligence By Raj Reddy
Toward Teleportation, Time Travel and Immortality By Raj Reddy
Online Chat with Ray Kurzweil and European Schoolnet By Ray Kurzweil
Biocosm, The New Scientific Theory of Evolution By James N. Gardner