#### Answer

An equation by which we can calculate the value of a dependent variable given the values of independent variables is called a model.
(please see details below)

#### Work Step by Step

A variable is a quantity whose numerical value varies under different circumstances.
We can say that its value may be dependent on the values of some other, independent, variables.
For example, Temperature at noon (at the main city square) will depend on the date, as some periods of the year are cooler than others. The independent variable here may be "days after Jan 1st."
An equation by which we can calculate the value of the dependant variable given the values of the independent variables is called a model.
This equation should yield approximately the same values as those measured at intermittent intervals.
(we may occassionaly read the temperature at noon, so we may have some data, but not for all days).
The model's role is to "fill the gaps" between measurements, and, more importantly,
provide a means of predicting future events,