The Default operator is used to provide a default value for a property or attribute of a class.

The syntax for using the Default operator is as follows:

 context ClassName
 inv: self.propertyName = defaultValue

Here, "ClassName" refers to the name of the class, "propertyName" refers to the name of the property or attribute, and "defaultValue" refers to the default value that is assigned to the property if no other value is provided.

For example, consider a class named "Person" that has a property named "age". We can use the Default operator to provide a default value of 18 for the "age" property, like this:

 context Person
 inv: self.age = 18

This means that if no age is explicitly assigned to a person object, it will automatically be set to 18.