# Domain

### From Glossary

The domain of a variable is a set of all possible values that can be assigned to the variable. When the domain contains numbers only, the variables are called numerical variables. The domain of a numerical variable may be further restricted to integers, rational numbers or real numbers. When the domain contains boolean values only, the variables are called boolean variables. When the domain contains an enumerated type of objects, the variables are called symbolic variables (e.g. a variable that represents a day of the week).

A common propagation technique in constraint programming is to dynamically remove values from the domain of a variable when it can be inferred that the value does not belong to any solution given the set of variable assignments that have already been made. See