Many times I can see these two different terms being used the other way around in articles. Simulation (προσομοίωση) is the process of modelling an event or process in a virtual environment. The model is aware that is being simulated and is different that the real one. It is used to represent the actual model/object. Emulation (εξομοίωση) on the other hand, is the process of creating the desired environment for an application, or an object in general, to act like being in the expected environment. For instance, a standard i386 Linux OS can be emulated on a i386 virtual machine that runs on PPC hardware. Emulation mimics what is excepted by the targeted object. The LHC can be simulated in a computer model. The first moments of the big bang will be emulated within the physical accelerator. Particles are not aware where they are physically.