Historically, the word had negative connotations:

…for Distinction Sake, a Deceiving by Words, is commonly called a Lye, and a Deceiving by Actions, Gestures, or Behavior, is called Simulation… Robert South (1643–1716)

However, the connection between simulation and dissembling later faded out and is now only of linguistic interest.

Simulation is used in many contexts, including the modeling of natural systems or human systems in order to gain insight into their functioning.Or, in the words of the Simulation article in Encyclopedia of Computer Science, "designing a model of a real or imagined system and conducting experiments with that model". Other contexts include simulation of technology for performance optimization, safety engineering, testing, training and education. Simulation can be used to show the eventual real effects of alternative conditions and courses of action.

Key issues in simulation include acquisition of valid source information about the referent, selection of key characteristics and behaviours, the use of simplifying approximations and assumptions within the simulation, and fidelity and validity of the simulation outcomes.

Classification and terminology

Physical and interactive simulation

Physical simulation refers to simulation in which physical objects are substituted for the real thing (some circles use the term for computer simulations modelling selected laws of physics, but this article doesn't). These physical objects are often chosen because they are smaller or cheaper than the actual object or system.

Interactive simulation is a special kind of physical simulation, often referred to as a human in the loop simulation, in which physical simulations include human operators, such as in a flight simulator or a driving simulator.

Human in the loop simulations can include a computer simulation as a so-called synthetic environmentThales defines synthetic environment as "the counterpart to simulated models of sensors, platforms and other active objects" for "the simulation of the external factors that affect them"1 while other vendors use the term for more visual, virtual reality-style simulators2. .