A mathematical representation in which every variable alters according to a mathematical formula, and not to random fluctuations.
It is one in which every set of variable states is uniquely determined by parameters in the model and by sets of previous states of these variables. Therefore, deterministic models perform the same way for a given set of initial conditions.
For instance a deterministic model can be applied to describe the predator-prey systems wherein the prey shows an age-specific vulnerability to predation.
Compare: stochastic model.