Attempting to predict aspects of the behaviour of some system

by creating an approximate (mathematical) model of it. This

can be done by physical modelling, by writing a

special-purpose computer program or using a more general

simulation package, probably still aimed at a particular kind

of simulation (e.g. structural engineering, fluid flow).

Typical examples are aircraft flight simlators or electronic

circuit simulators. A great many simulation languages exist,

e.g. Simula.