Inheritance function mix-in Do minimum in itself, and fully rely on what succeeded from the ancestor or the relative to deal the rest matter. In the real world, It should be an unpleasant fellow. Turned to establish a new class which adds the ((function|Function)) to a certain class. Inheritance is effective to express the relation of is-a. For instance, "Student" class which describes the character of the general student can be succeeded to "Department of Engineering student (who is afflicted with the experiment)" class. When there is no is-a relation and the situation only shares the character and the function, it is assumed preferable to use ((Mix-in)).